trait Map[K, V] extends Iterable[(K, V)] with collection.Map[K, V] with MapLike[K, V, Map[K, V]]
A base trait for maps that can be mutated.
Implementation note:
This trait provides most of the operations of a mutable Map
independently of its representation. It is typically inherited by
concrete implementations of maps.
To implement a concrete mutable map, you need to provide implementations of the following methods:
def get(key: K): Option[V] def iterator: Iterator[(K, V)] def += (kv: (K, V)): This def -= (key: K): This
If you wish that methods like take
, drop
, filter
also return the same kind of map
you should also override:
def empty: This
It is also good idea to override methods foreach
and
size
for efficiency.
- Source
- Map.scala
- Since
1.0
- Alphabetic
- By Inheritance
- Map
- MapLike
- Cloneable
- Cloneable
- Cloneable
- Shrinkable
- Builder
- Growable
- Clearable
- Map
- MapLike
- Subtractable
- PartialFunction
- Function1
- GenMap
- GenMapLike
- Iterable
- Iterable
- IterableLike
- Equals
- GenIterable
- GenIterableLike
- Traversable
- Mutable
- Traversable
- GenTraversable
- GenericTraversableTemplate
- TraversableLike
- GenTraversableLike
- Parallelizable
- TraversableOnce
- GenTraversableOnce
- FilterMonadic
- HasNewBuilder
- AnyRef
- Any
- by CollectionsHaveToParArray
- by MonadOps
- by any2stringadd
- by StringFormat
- by Ensuring
- by ArrowAssoc
- by alternateImplicit
- Hide All
- Show All
- Public
- All
Type Members
-
class
DefaultKeySet extends AbstractSet[K] with Set[K] with Serializable
The implementation class of the set returned by
keySet
.The implementation class of the set returned by
keySet
.- Attributes
- protected
- Definition Classes
- MapLike
- Annotations
- @SerialVersionUID()
-
class
DefaultValuesIterable extends AbstractIterable[V] with Iterable[V] with Serializable
The implementation class of the iterable returned by
values
.The implementation class of the iterable returned by
values
.- Attributes
- protected
- Definition Classes
- MapLike
-
class
FilteredKeys extends AbstractMap[K, V] with DefaultMap[K, V]
- Attributes
- protected
- Definition Classes
- MapLike
-
class
MappedValues[W] extends AbstractMap[K, W] with DefaultMap[K, W]
- Attributes
- protected
- Definition Classes
- MapLike
-
class
WithFilter extends FilterMonadic[A, Repr]
A class supporting filtered operations.
A class supporting filtered operations. Instances of this class are returned by method
withFilter
.- Definition Classes
- TraversableLike
-
type
Self = Map[K, V]
The type implementing this traversable
The type implementing this traversable
- Attributes
- protected[this]
- Definition Classes
- TraversableLike
Abstract Value Members
-
abstract
def
+=(kv: (K, V)): Map.this.type
Adds a new key/value pair to this map.
-
abstract
def
-=(key: K): Map.this.type
Removes a key from this map.
Removes a key from this map.
- key
the key to be removed
- returns
the map itself.
- Definition Classes
- MapLike → Shrinkable
-
abstract
def
get(key: K): Option[V]
Optionally returns the value associated with a key.
Optionally returns the value associated with a key.
- key
the key value
- returns
an option value containing the value associated with
key
in this map, orNone
if none exists.
- Definition Classes
- MapLike → GenMapLike
-
abstract
def
iterator: Iterator[(K, V)]
Creates a new iterator over all key/value pairs of this map
Creates a new iterator over all key/value pairs of this map
- returns
the new iterator
- Definition Classes
- MapLike → IterableLike → GenIterableLike
Concrete Value Members
-
final
def
!=(arg0: Any): Boolean
Test two objects for inequality.
Test two objects for inequality.
- returns
true
if !(this == that), false otherwise.
- Definition Classes
- AnyRef → Any
-
final
def
##(): Int
Equivalent to
x.hashCode
except for boxed numeric types andnull
.Equivalent to
x.hashCode
except for boxed numeric types andnull
. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. Fornull
returns a hashcode wherenull.hashCode
throws aNullPointerException
.- returns
a hash value consistent with ==
- Definition Classes
- AnyRef → Any
-
def
+[V1 >: V](elem1: (K, V1), elem2: (K, V1), elems: (K, V1)*): Map[K, V1]
Creates a new map containing two or more key/value mappings and all the key/value mappings of this map.
Creates a new map containing two or more key/value mappings and all the key/value mappings of this map.
Specified mappings will override existing mappings from this map with the same keys.
- V1
the type of the added values
- elem1
the first element to add.
- elem2
the second element to add.
- elems
the remaining elements to add.
- returns
a new map containing mappings of this map and two or more specified mappings.
-
def
+[V1 >: V](kv: (K, V1)): Map[K, V1]
Creates a new map containing a new key/value mapping and all the key/value mappings of this map.
Creates a new map containing a new key/value mapping and all the key/value mappings of this map.
Mapping
kv
will override existing mappings from this map with the same key.- V1
the type of the value in the key/value pair.
- kv
the key/value mapping to be added
- returns
a new map containing mappings of this map and the mapping
kv
.
- Definition Classes
- MapLike → MapLike → GenMapLike
- Annotations
- @migration
- Migration
(Changed in version 2.8.0)
+
creates a new map. Use+=
to add an element to this map and return that map itself.
-
def
++[V1 >: V](xs: GenTraversableOnce[(K, V1)]): Map[K, V1]
Creates a new map containing the key/value mappings provided by the specified traversable object and all the key/value mappings of this map.
Creates a new map containing the key/value mappings provided by the specified traversable object and all the key/value mappings of this map.
Note that existing mappings from this map with the same key as those in
xs
will be overridden.- V1
the type of the added values
- xs
the traversable object.
- returns
a new map containing mappings of this map and those provided by
xs
.
-
def
++[B >: (K, V), That](that: GenTraversableOnce[B])(implicit bf: CanBuildFrom[Map[K, V], B, That]): That
Returns a new traversable collection containing the elements from the left hand operand followed by the elements from the right hand operand.
Returns a new traversable collection containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the traversable collection is the most specific superclass encompassing the element types of the two operands.
- B
the element type of the returned collection.
- That
the class of the returned collection. Where possible,
That
is the same class as the current collection classRepr
, but this depends on the element typeB
being admissible for that class, which means that an implicit instance of typeCanBuildFrom[Repr, B, That]
is found.- that
the traversable to append.
- bf
an implicit value of class
CanBuildFrom
which determines the result classThat
from the current representation typeRepr
and the new element typeB
.- returns
a new collection of type
That
which contains all elements of this traversable collection followed by all elements ofthat
.
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
++:[B >: (K, V), That](that: collection.Traversable[B])(implicit bf: CanBuildFrom[Map[K, V], B, That]): That
As with
++
, returns a new collection containing the elements from the left operand followed by the elements from the right operand.As with
++
, returns a new collection containing the elements from the left operand followed by the elements from the right operand.It differs from
++
in that the right operand determines the type of the resulting collection rather than the left one. Mnemonic: the COLon is on the side of the new COLlection type.Example:
scala> val x = List(1) x: List[Int] = List(1) scala> val y = LinkedList(2) y: scala.collection.mutable.LinkedList[Int] = LinkedList(2) scala> val z = x ++: y z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)
This overload exists because: for the implementation of
++:
we should reuse that of++
because many collections override it with more efficient versions.Since
TraversableOnce
has no++
method, we have to implement that directly, butTraversable
and down can use the overload.- B
the element type of the returned collection.
- That
the class of the returned collection. Where possible,
That
is the same class as the current collection classRepr
, but this depends on the element typeB
being admissible for that class, which means that an implicit instance of typeCanBuildFrom[Repr, B, That]
is found.- that
the traversable to append.
- bf
an implicit value of class
CanBuildFrom
which determines the result classThat
from the current representation typeRepr
and the new element typeB
.- returns
a new collection of type
That
which contains all elements of this traversable collection followed by all elements ofthat
.
- Definition Classes
- TraversableLike
-
def
++:[B](that: TraversableOnce[B]): Map[B]
[use case] As with
++
, returns a new collection containing the elements from the left operand followed by the elements from the right operand.[use case]As with
++
, returns a new collection containing the elements from the left operand followed by the elements from the right operand.It differs from
++
in that the right operand determines the type of the resulting collection rather than the left one. Mnemonic: the COLon is on the side of the new COLlection type.Example:
scala> val x = List(1) x: List[Int] = List(1) scala> val y = LinkedList(2) y: scala.collection.mutable.LinkedList[Int] = LinkedList(2) scala> val z = x ++: y z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)
- B
the element type of the returned collection.
- that
the traversable to append.
- returns
a new mutable map which contains all elements of this mutable map followed by all elements of
that
.
- Definition Classes
- TraversableLike
Full Signaturedef ++:[B >: (K, V), That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Map[K, V], B, That]): That
-
def
++=(xs: TraversableOnce[(K, V)]): Map.this.type
adds all elements produced by a TraversableOnce to this growable collection.
adds all elements produced by a TraversableOnce to this growable collection.
- xs
the TraversableOnce producing the elements to add.
- returns
the growable collection itself.
- Definition Classes
- Growable
-
def
+=(elem1: (K, V), elem2: (K, V), elems: (K, V)*): Map.this.type
adds two or more elements to this growable collection.
adds two or more elements to this growable collection.
- elem1
the first element to add.
- elem2
the second element to add.
- elems
the remaining elements to add.
- returns
the growable collection itself
- Definition Classes
- Growable
-
def
-(elem1: K, elem2: K, elems: K*): Map[K, V]
Creates a new map with all the key/value mappings of this map except mappings with keys equal to any of the two or more specified keys.
Creates a new map with all the key/value mappings of this map except mappings with keys equal to any of the two or more specified keys.
- elem1
the first element to remove.
- elem2
the second element to remove.
- elems
the remaining elements to remove.
- returns
a new map containing all the mappings of this map except mappings with a key equal to
elem1
,elem2
or any ofelems
.
- Definition Classes
- MapLike → Subtractable
- Annotations
- @migration
- Migration
(Changed in version 2.8.0)
-
creates a new map. Use-=
to remove an element from this map and return that map itself.
-
def
-(key: K): Map[K, V]
Creates a new map with all the key/value mappings of this map except the key/value mapping with the specified key.
Creates a new map with all the key/value mappings of this map except the key/value mapping with the specified key.
- key
the key to be removed
- returns
a new map with all the mappings of this map except that with a key
key
.
- Definition Classes
- MapLike → MapLike → Subtractable → GenMapLike
- Annotations
- @migration
- Migration
(Changed in version 2.8.0)
-
creates a new map. Use-=
to remove an element from this map and return that map itself.
-
def
--(xs: GenTraversableOnce[K]): Map[K, V]
Creates a new map with all the key/value mappings of this map except mappings with keys equal to any of those provided by the specified traversable object.
Creates a new map with all the key/value mappings of this map except mappings with keys equal to any of those provided by the specified traversable object.
- xs
the traversable object.
- returns
a new map with all the key/value mappings of this map except mappings with a key equal to a key from
xs
.
- Definition Classes
- MapLike → Subtractable
- Annotations
- @migration
- Migration
(Changed in version 2.8.0)
--
creates a new map. Use--=
to remove an element from this map and return that map itself.
-
def
--=(xs: TraversableOnce[K]): Map.this.type
Removes all elements produced by an iterator from this shrinkable collection.
Removes all elements produced by an iterator from this shrinkable collection.
- xs
the iterator producing the elements to remove.
- returns
the shrinkable collection itself
- Definition Classes
- Shrinkable
-
def
-=(elem1: K, elem2: K, elems: K*): Map.this.type
Removes two or more elements from this shrinkable collection.
Removes two or more elements from this shrinkable collection.
- elem1
the first element to remove.
- elem2
the second element to remove.
- elems
the remaining elements to remove.
- returns
the shrinkable collection itself
- Definition Classes
- Shrinkable
-
def
->[B](y: B): (Map[K, V], B)
- Implicit
- This member is added by an implicit conversion from Map[K, V] to ArrowAssoc[Map[K, V]] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
- Annotations
- @inline()
-
final
def
==(arg0: Any): Boolean
The expression
x == that
is equivalent toif (x eq null) that eq null else x.equals(that)
.The expression
x == that
is equivalent toif (x eq null) that eq null else x.equals(that)
.- returns
true
if the receiver object is equivalent to the argument;false
otherwise.
- Definition Classes
- AnyRef → Any
-
def
addString(b: scala.StringBuilder, start: String, sep: String, end: String): scala.StringBuilder
Appends all bindings of this map to a string builder using start, end, and separator strings.
Appends all bindings of this map to a string builder using start, end, and separator strings. The written text begins with the string
start
and ends with the stringend
. Inside, the string representations of all bindings of this map in the form ofkey -> value
are separated by the stringsep
.- b
the builder to which strings are appended.
- start
the starting string.
- sep
the separator string.
- end
the ending string.
- returns
the string builder
b
to which elements were appended.
- Definition Classes
- MapLike → TraversableOnce
-
def
addString(b: scala.StringBuilder): scala.StringBuilder
Appends all elements of this traversable or iterator to a string builder.
Appends all elements of this traversable or iterator to a string builder. The written text consists of the string representations (w.r.t. the method
toString
) of all elements of this traversable or iterator without any separator string.Example:
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = new StringBuilder() b: StringBuilder = scala> val h = a.addString(b) h: StringBuilder = 1234
- b
the string builder to which elements are appended.
- returns
the string builder
b
to which elements were appended.
- Definition Classes
- TraversableOnce
-
def
addString(b: scala.StringBuilder, sep: String): scala.StringBuilder
Appends all elements of this traversable or iterator to a string builder using a separator string.
Appends all elements of this traversable or iterator to a string builder using a separator string. The written text consists of the string representations (w.r.t. the method
toString
) of all elements of this traversable or iterator, separated by the stringsep
.Example:
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = new StringBuilder() b: StringBuilder = scala> a.addString(b, ", ") res0: StringBuilder = 1, 2, 3, 4
- b
the string builder to which elements are appended.
- sep
the separator string.
- returns
the string builder
b
to which elements were appended.
- Definition Classes
- TraversableOnce
-
def
aggregate[B](z: ⇒ B)(seqop: (B, (K, V)) ⇒ B, combop: (B, B) ⇒ B): B
Aggregates the results of applying an operator to subsequent elements.
Aggregates the results of applying an operator to subsequent elements.
This is a more general form of
fold
andreduce
. It is similar tofoldLeft
in that it doesn't require the result to be a supertype of the element type. In addition, it allows parallel collections to be processed in chunks, and then combines the intermediate results.aggregate
splits the traversable or iterator into partitions and processes each partition by sequentially applyingseqop
, starting withz
(likefoldLeft
). Those intermediate results are then combined by usingcombop
(likefold
). The implementation of this operation may operate on an arbitrary number of collection partitions (even 1), socombop
may be invoked an arbitrary number of times (even 0).As an example, consider summing up the integer values of a list of chars. The initial value for the sum is 0. First,
seqop
transforms each input character to an Int and adds it to the sum (of the partition). Then,combop
just needs to sum up the intermediate results of the partitions:List('a', 'b', 'c').aggregate(0)({ (sum, ch) => sum + ch.toInt }, { (p1, p2) => p1 + p2 })
- B
the type of accumulated results
- z
the initial value for the accumulated result of the partition - this will typically be the neutral element for the
seqop
operator (e.g.Nil
for list concatenation or0
for summation) and may be evaluated more than once- seqop
an operator used to accumulate results within a partition
- combop
an associative operator used to combine results from different partitions
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
andThen[C](k: (V) ⇒ C): PartialFunction[K, C]
Composes this partial function with a transformation function that gets applied to results of this partial function.
Composes this partial function with a transformation function that gets applied to results of this partial function.
- C
the result type of the transformation function.
- k
the transformation function
- returns
a partial function with the same domain as this partial function, which maps arguments
x
tok(this(x))
.
- Definition Classes
- PartialFunction → Function1
-
def
apply(key: K): V
Retrieves the value which is associated with the given key.
Retrieves the value which is associated with the given key. This method invokes the
default
method of the map if there is no mapping from the given key to a value. Unless overridden, thedefault
method throws aNoSuchElementException
.- key
the key
- returns
the value associated with the given key, or the result of the map's
default
method, if none exists.
- Definition Classes
- MapLike → GenMapLike → Function1
-
def
applyOrElse[K1 <: K, V1 >: V](x: K1, default: (K1) ⇒ V1): V1
Applies this partial function to the given argument when it is contained in the function domain.
Applies this partial function to the given argument when it is contained in the function domain. Applies fallback function where this partial function is not defined.
Note that expression
pf.applyOrElse(x, default)
is equivalent toif(pf isDefinedAt x) pf(x) else default(x)
except that
applyOrElse
method can be implemented more efficiently. For all partial function literals the compiler generates anapplyOrElse
implementation which avoids double evaluation of pattern matchers and guards. This makesapplyOrElse
the basis for the efficient implementation for many operations and scenarios, such as:- combining partial functions into
orElse
/andThen
chains does not lead to excessiveapply
/isDefinedAt
evaluation lift
andunlift
do not evaluate source functions twice on each invocationrunWith
allows efficient imperative-style combining of partial functions with conditionally applied actions
For non-literal partial function classes with nontrivial
isDefinedAt
method it is recommended to overrideapplyOrElse
with custom implementation that avoids doubleisDefinedAt
evaluation. This may result in better performance and more predictable behavior w.r.t. side effects.- x
the function argument
- default
the fallback function
- returns
the result of this function or fallback function application.
- Definition Classes
- MapLike → PartialFunction
- Since
2.10
- combining partial functions into
-
final
def
asInstanceOf[T0]: T0
Cast the receiver object to be of type
T0
.Cast the receiver object to be of type
T0
.Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression
1.asInstanceOf[String]
will throw aClassCastException
at runtime, while the expressionList(1).asInstanceOf[List[String]]
will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.- returns
the receiver object.
- Definition Classes
- Any
- Exceptions thrown
ClassCastException
if the receiver object is not an instance of the erasure of typeT0
.
-
def
canEqual(that: Any): Boolean
Method called from equality methods, so that user-defined subclasses can refuse to be equal to other collections of the same kind.
Method called from equality methods, so that user-defined subclasses can refuse to be equal to other collections of the same kind.
- that
The object with which this iterable collection should be compared
- returns
true
, if this iterable collection can possibly equalthat
,false
otherwise. The test takes into consideration only the run-time types of objects but ignores their elements.
- Definition Classes
- IterableLike → Equals
-
def
clear(): Unit
Removes all bindings from the map.
-
def
clone(): Map[K, V]
Create a copy of the receiver object.
-
def
collect[B](pf: PartialFunction[A, B]): Map[B]
[use case] Builds a new collection by applying a partial function to all elements of this mutable map on which the function is defined.
[use case]Builds a new collection by applying a partial function to all elements of this mutable map on which the function is defined.
- B
the element type of the returned collection.
- pf
the partial function which filters and maps the mutable map.
- returns
a new mutable map resulting from applying the given partial function
pf
to each element on which it is defined and collecting the results. The order of the elements is preserved.
- Definition Classes
- TraversableLike → GenTraversableLike
Full Signaturedef collect[B, That](pf: PartialFunction[(K, V), B])(implicit bf: CanBuildFrom[Map[K, V], B, That]): That
-
def
collectFirst[B](pf: PartialFunction[(K, V), B]): Option[B]
Finds the first element of the traversable or iterator for which the given partial function is defined, and applies the partial function to it.
Finds the first element of the traversable or iterator for which the given partial function is defined, and applies the partial function to it.
Note: may not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- pf
the partial function
- returns
an option value containing pf applied to the first value for which it is defined, or
None
if none exists.
- Definition Classes
- TraversableOnce
Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)
Example: -
def
companion: GenericCompanion[Iterable]
The factory companion object that builds instances of class Iterable.
The factory companion object that builds instances of class Iterable. (or its
Iterable
superclass where class Iterable is not aSeq
.)- Definition Classes
- Iterable → Iterable → GenIterable → Traversable → Traversable → GenTraversable → GenericTraversableTemplate
-
def
compose[A](g: (A) ⇒ K): (A) ⇒ V
Composes two instances of Function1 in a new Function1, with this function applied last.
Composes two instances of Function1 in a new Function1, with this function applied last.
- A
the type to which function
g
can be applied- g
a function A => T1
- returns
a new function
f
such thatf(x) == apply(g(x))
- Definition Classes
- Function1
- Annotations
- @unspecialized()
-
def
contains(key: K): Boolean
Tests whether this map contains a binding for a key.
Tests whether this map contains a binding for a key.
- key
the key
- returns
true
if there is a binding forkey
in this map,false
otherwise.
- Definition Classes
- MapLike → GenMapLike
-
def
copyToArray(xs: Array[A], start: Int, len: Int): Unit
[use case] Copies the elements of this mutable map to an array.
[use case]Copies the elements of this mutable map to an array. Fills the given array
xs
with at mostlen
elements of this mutable map, starting at positionstart
. Copying will stop once either the end of the current mutable map is reached, or the end of the target array is reached, orlen
elements have been copied.- xs
the array to fill.
- start
the starting index.
- len
the maximal number of elements to copy.
- Definition Classes
- IterableLike → TraversableLike → TraversableOnce → GenTraversableOnce
-
def
copyToArray(xs: Array[A]): Unit
[use case] Copies the elements of this mutable map to an array.
[use case]Copies the elements of this mutable map to an array. Fills the given array
xs
with values of this mutable map. Copying will stop once either the end of the current mutable map is reached, or the end of the target array is reached.- xs
the array to fill.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
copyToArray(xs: Array[A], start: Int): Unit
[use case] Copies the elements of this mutable map to an array.
[use case]Copies the elements of this mutable map to an array. Fills the given array
xs
with values of this mutable map, beginning at indexstart
. Copying will stop once either the end of the current mutable map is reached, or the end of the target array is reached.- xs
the array to fill.
- start
the starting index.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
copyToBuffer[B >: (K, V)](dest: Buffer[B]): Unit
Copies all elements of this traversable or iterator to a buffer.
Copies all elements of this traversable or iterator to a buffer.
Note: will not terminate for infinite-sized collections.
- dest
The buffer to which elements are copied.
- Definition Classes
- TraversableOnce
-
def
count(p: ((K, V)) ⇒ Boolean): Int
Counts the number of elements in the traversable or iterator which satisfy a predicate.
Counts the number of elements in the traversable or iterator which satisfy a predicate.
- p
the predicate used to test elements.
- returns
the number of elements satisfying the predicate
p
.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
default(key: K): V
Defines the default value computation for the map, returned when a key is not found The method implemented here throws an exception, but it might be overridden in subclasses.
Defines the default value computation for the map, returned when a key is not found The method implemented here throws an exception, but it might be overridden in subclasses.
- key
the given key value for which a binding is missing.
- Definition Classes
- MapLike → GenMapLike
- Exceptions thrown
-
def
drop(n: Int): Map[K, V]
Selects all elements except first n ones.
Selects all elements except first n ones.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- n
the number of elements to drop from this iterable collection.
- returns
a iterable collection consisting of all elements of this iterable collection except the first
n
ones, or else the empty iterable collection, if this iterable collection has less thann
elements. Ifn
is negative, don't drop any elements.
- Definition Classes
- IterableLike → TraversableLike → GenTraversableLike
-
def
dropRight(n: Int): Map[K, V]
Selects all elements except last n ones.
Selects all elements except last n ones.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- n
The number of elements to take
- returns
a iterable collection consisting of all elements of this iterable collection except the last
n
ones, or else the empty iterable collection, if this iterable collection has less thann
elements.
- Definition Classes
- IterableLike
-
def
dropWhile(p: ((K, V)) ⇒ Boolean): Map[K, V]
Drops longest prefix of elements that satisfy a predicate.
Drops longest prefix of elements that satisfy a predicate.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
the longest suffix of this traversable collection whose first element does not satisfy the predicate
p
.
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
empty: Map[K, V]
The empty map of the same type as this map
-
def
ensuring(cond: (Map[K, V]) ⇒ Boolean, msg: ⇒ Any): Map[K, V]
- Implicit
- This member is added by an implicit conversion from Map[K, V] to Ensuring[Map[K, V]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
def
ensuring(cond: (Map[K, V]) ⇒ Boolean): Map[K, V]
- Implicit
- This member is added by an implicit conversion from Map[K, V] to Ensuring[Map[K, V]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
def
ensuring(cond: Boolean, msg: ⇒ Any): Map[K, V]
- Implicit
- This member is added by an implicit conversion from Map[K, V] to Ensuring[Map[K, V]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
def
ensuring(cond: Boolean): Map[K, V]
- Implicit
- This member is added by an implicit conversion from Map[K, V] to Ensuring[Map[K, V]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
final
def
eq(arg0: AnyRef): Boolean
Tests whether the argument (
that
) is a reference to the receiver object (this
).Tests whether the argument (
that
) is a reference to the receiver object (this
).The
eq
method implements an equivalence relation on non-null instances ofAnyRef
, and has three additional properties:- It is consistent: for any non-null instances
x
andy
of typeAnyRef
, multiple invocations ofx.eq(y)
consistently returnstrue
or consistently returnsfalse
. - For any non-null instance
x
of typeAnyRef
,x.eq(null)
andnull.eq(x)
returnsfalse
. null.eq(null)
returnstrue
.
When overriding the
equals
orhashCode
methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2
), they should be equal to each other (o1 == o2
) and they should hash to the same value (o1.hashCode == o2.hashCode
).- returns
true
if the argument is a reference to the receiver object;false
otherwise.
- Definition Classes
- AnyRef
- It is consistent: for any non-null instances
-
def
equals(that: Any): Boolean
Compares two maps structurally; i.e., checks if all mappings contained in this map are also contained in the other map, and vice versa.
Compares two maps structurally; i.e., checks if all mappings contained in this map are also contained in the other map, and vice versa.
- that
the other map
- returns
true
if both maps contain exactly the same mappings,false
otherwise.
- Definition Classes
- GenMapLike → Equals → AnyRef → Any
-
def
exists(p: ((K, V)) ⇒ Boolean): Boolean
Tests whether a predicate holds for at least one element of this iterable collection.
Tests whether a predicate holds for at least one element of this iterable collection.
Note: may not terminate for infinite-sized collections.
- p
the predicate used to test elements.
- returns
false
if this iterable collection is empty, otherwisetrue
if the given predicatep
holds for some of the elements of this iterable collection, otherwisefalse
- Definition Classes
- IterableLike → TraversableLike → TraversableOnce → GenTraversableOnce
-
def
filter(p: ((K, V)) ⇒ Boolean): Map[K, V]
Selects all elements of this traversable collection which satisfy a predicate.
Selects all elements of this traversable collection which satisfy a predicate.
- p
the predicate used to test elements.
- returns
a new traversable collection consisting of all elements of this traversable collection that satisfy the given predicate
p
. The order of the elements is preserved.
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
filterKeys(p: (K) ⇒ Boolean): collection.Map[K, V]
Filters this map by retaining only keys satisfying a predicate.
Filters this map by retaining only keys satisfying a predicate.
Note: the predicate must accept any key of type
K
, not just those already present in the map, as the predicate is tested before the underlying map is queried.- p
the predicate used to test keys
- returns
an immutable map consisting only of those key value pairs of this map where the key satisfies the predicate
p
. The resulting map wraps the original map without copying any elements.
- Definition Classes
- MapLike → GenMapLike
-
def
filterNot(p: ((K, V)) ⇒ Boolean): Map[K, V]
Returns a new map obtained by removing all key/value pairs for which the predicate
p
returnstrue
.Returns a new map obtained by removing all key/value pairs for which the predicate
p
returnstrue
.Note: This method works by successively removing elements for which the predicate is true from this set. If removal is slow, or you expect that most elements of the set will be removed, you might consider using
filter
with a negated predicate instead.- p
A predicate over key-value pairs
- returns
A new map containing elements not satisfying the predicate.
- Definition Classes
- MapLike → TraversableLike → GenTraversableLike
-
def
finalize(): Unit
Called by the garbage collector on the receiver object when there are no more references to the object.
Called by the garbage collector on the receiver object when there are no more references to the object.
The details of when and if the
finalize
method is invoked, as well as the interaction betweenfinalize
and non-local returns and exceptions, are all platform dependent.- Attributes
- protected[lang]
- Definition Classes
- AnyRef
- Annotations
- @throws( classOf[java.lang.Throwable] )
- Note
not specified by SLS as a member of AnyRef
-
def
find(p: ((K, V)) ⇒ Boolean): Option[(K, V)]
Finds the first element of the iterable collection satisfying a predicate, if any.
Finds the first element of the iterable collection satisfying a predicate, if any.
Note: may not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- p
the predicate used to test elements.
- returns
an option value containing the first element in the iterable collection that satisfies
p
, orNone
if none exists.
- Definition Classes
- IterableLike → TraversableLike → TraversableOnce → GenTraversableOnce
-
def
flatMap[B](f: (A) ⇒ GenTraversableOnce[B]): Map[B]
[use case] Builds a new collection by applying a function to all elements of this mutable map and using the elements of the resulting collections.
[use case]Builds a new collection by applying a function to all elements of this mutable map and using the elements of the resulting collections.
For example:
def getWords(lines: Seq[String]): Seq[String] = lines flatMap (line => line split "\\W+")
The type of the resulting collection is guided by the static type of mutable map. This might cause unexpected results sometimes. For example:
// lettersOf will return a Seq[Char] of likely repeated letters, instead of a Set def lettersOf(words: Seq[String]) = words flatMap (word => word.toSet) // lettersOf will return a Set[Char], not a Seq def lettersOf(words: Seq[String]) = words.toSet flatMap (word => word.toSeq) // xs will be an Iterable[Int] val xs = Map("a" -> List(11,111), "b" -> List(22,222)).flatMap(_._2) // ys will be a Map[Int, Int] val ys = Map("a" -> List(1 -> 11,1 -> 111), "b" -> List(2 -> 22,2 -> 222)).flatMap(_._2)
- B
the element type of the returned collection.
- f
the function to apply to each element.
- returns
a new mutable map resulting from applying the given collection-valued function
f
to each element of this mutable map and concatenating the results.
- Definition Classes
- TraversableLike → GenTraversableLike → FilterMonadic
Full Signaturedef flatMap[B, That](f: ((K, V)) ⇒ GenTraversableOnce[B])(implicit bf: CanBuildFrom[Map[K, V], B, That]): That
-
def
flatten[B]: Map[B]
[use case] Converts this mutable map of traversable collections into a mutable map formed by the elements of these traversable collections.
[use case]Converts this mutable map of traversable collections into a mutable map formed by the elements of these traversable collections.
The resulting collection's type will be guided by the static type of mutable map. For example:
val xs = List( Set(1, 2, 3), Set(1, 2, 3) ).flatten // xs == List(1, 2, 3, 1, 2, 3) val ys = Set( List(1, 2, 3), List(3, 2, 1) ).flatten // ys == Set(1, 2, 3)
- B
the type of the elements of each traversable collection.
- returns
a new mutable map resulting from concatenating all element mutable maps.
- Definition Classes
- GenericTraversableTemplate
Full Signaturedef flatten[B](implicit asTraversable: ((K, V)) ⇒ GenTraversableOnce[B]): Iterable[B]
-
def
fold[A1 >: (K, V)](z: A1)(op: (A1, A1) ⇒ A1): A1
Folds the elements of this traversable or iterator using the specified associative binary operator.
Folds the elements of this traversable or iterator using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
Note: will not terminate for infinite-sized collections.
- A1
a type parameter for the binary operator, a supertype of
A
.- z
a neutral element for the fold operation; may be added to the result an arbitrary number of times, and must not change the result (e.g.,
Nil
for list concatenation, 0 for addition, or 1 for multiplication).- op
a binary operator that must be associative.
- returns
the result of applying the fold operator
op
between all the elements andz
, orz
if this traversable or iterator is empty.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
foldLeft[B](z: B)(op: (B, (K, V)) ⇒ B): B
Applies a binary operator to a start value and all elements of this traversable or iterator, going left to right.
Applies a binary operator to a start value and all elements of this traversable or iterator, going left to right.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
- B
the result type of the binary operator.
- z
the start value.
- op
the binary operator.
- returns
the result of inserting
op
between consecutive elements of this traversable or iterator, going left to right with the start valuez
on the left:op(...op(z, x_1), x_2, ..., x_n)
where
x1, ..., xn
are the elements of this traversable or iterator. Returnsz
if this traversable or iterator is empty.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
foldRight[B](z: B)(op: ((K, V), B) ⇒ B): B
Applies a binary operator to all elements of this iterable collection and a start value, going right to left.
Applies a binary operator to all elements of this iterable collection and a start value, going right to left.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.
- B
the result type of the binary operator.
- z
the start value.
- op
the binary operator.
- returns
the result of inserting
op
between consecutive elements of this iterable collection, going right to left with the start valuez
on the right:op(x_1, op(x_2, ... op(x_n, z)...))
where
x1, ..., xn
are the elements of this iterable collection. Returnsz
if this iterable collection is empty.
- Definition Classes
- IterableLike → TraversableOnce → GenTraversableOnce
-
def
forall(p: ((K, V)) ⇒ Boolean): Boolean
Tests whether a predicate holds for all elements of this iterable collection.
Tests whether a predicate holds for all elements of this iterable collection.
Note: may not terminate for infinite-sized collections.
- p
the predicate used to test elements.
- returns
true
if this iterable collection is empty or the given predicatep
holds for all elements of this iterable collection, otherwisefalse
.
- Definition Classes
- IterableLike → TraversableLike → TraversableOnce → GenTraversableOnce
-
def
foreach(f: ((K, V)) ⇒ Unit): Unit
[use case] Applies a function
f
to all elements of this mutable map.[use case]Applies a function
f
to all elements of this mutable map.Note: this method underlies the implementation of most other bulk operations. Subclasses should re-implement this method if a more efficient implementation exists.
- f
the function that is applied for its side-effect to every element. The result of function
f
is discarded.
- Definition Classes
- IterableLike → TraversableLike → GenTraversableLike → TraversableOnce → GenTraversableOnce → FilterMonadic
Full Signaturedef foreach[U](f: ((K, V)) ⇒ U): Unit
-
def
genericBuilder[B]: Builder[B, Iterable[B]]
The generic builder that builds instances of Traversable at arbitrary element types.
The generic builder that builds instances of Traversable at arbitrary element types.
- Definition Classes
- GenericTraversableTemplate
-
final
def
getClass(): Class[_]
Returns the runtime class representation of the object.
-
def
getOrElse(key: K, default: ⇒ V): V
[use case] Returns the value associated with a key, or a default value if the key is not contained in the map.
[use case]Returns the value associated with a key, or a default value if the key is not contained in the map.
- key
the key.
- default
a computation that yields a default value in case no binding for
key
is found in the map.- returns
the value associated with
key
if it exists, otherwise the result of thedefault
computation.
- Definition Classes
- MapLike → GenMapLike
Full Signaturedef getOrElse[V1 >: V](key: K, default: ⇒ V1): V1
-
def
getOrElseUpdate(key: K, op: ⇒ V): V
If given key is already in this map, returns associated value.
If given key is already in this map, returns associated value.
Otherwise, computes value from given expression
op
, stores with key in map and returns that value.Concurrent map implementations may evaluate the expression
op
multiple times, or may evaluateop
without inserting the result.- key
the key to test
- op
the computation yielding the value to associate with
key
, ifkey
is previously unbound.- returns
the value associated with key (either previously or as a result of executing the method).
- Definition Classes
- MapLike
-
def
groupBy[K](f: ((K, V)) ⇒ K): immutable.Map[K, Map[K, V]]
Partitions this traversable collection into a map of traversable collections according to some discriminator function.
Partitions this traversable collection into a map of traversable collections according to some discriminator function.
Note: this method is not re-implemented by views. This means when applied to a view it will always force the view and return a new traversable collection.
- K
the type of keys returned by the discriminator function.
- f
the discriminator function.
- returns
A map from keys to traversable collections such that the following invariant holds:
(xs groupBy f)(k) = xs filter (x => f(x) == k)
That is, every key
k
is bound to a traversable collection of those elementsx
for whichf(x)
equalsk
.
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
grouped(size: Int): Iterator[Map[K, V]]
Partitions elements in fixed size iterable collections.
Partitions elements in fixed size iterable collections.
- size
the number of elements per group
- returns
An iterator producing iterable collections of size
size
, except the last will be less than sizesize
if the elements don't divide evenly.
- Definition Classes
- IterableLike
- See also
scala.collection.Iterator, method
grouped
-
def
hasDefiniteSize: Boolean
Tests whether this traversable collection is known to have a finite size.
Tests whether this traversable collection is known to have a finite size. All strict collections are known to have finite size. For a non-strict collection such as
Stream
, the predicate returnstrue
if all elements have been computed. It returnsfalse
if the stream is not yet evaluated to the end. Non-empty Iterators usually returnfalse
even if they were created from a collection with a known finite size.Note: many collection methods will not work on collections of infinite sizes. The typical failure mode is an infinite loop. These methods always attempt a traversal without checking first that
hasDefiniteSize
returnstrue
. However, checkinghasDefiniteSize
can provide an assurance that size is well-defined and non-termination is not a concern.- returns
true
if this collection is known to have finite size,false
otherwise.
- Definition Classes
- TraversableLike → TraversableOnce → GenTraversableOnce
-
def
hashCode(): Int
The hashCode method for reference types.
The hashCode method for reference types. See hashCode in scala.Any.
- returns
the hash code value for this object.
- Definition Classes
- GenMapLike → AnyRef → Any
-
def
head: (K, V)
Selects the first element of this iterable collection.
Selects the first element of this iterable collection.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
the first element of this iterable collection.
- Definition Classes
- IterableLike → TraversableLike → GenTraversableLike
- Exceptions thrown
NoSuchElementException
if the iterable collection is empty.
-
def
headOption: Option[(K, V)]
Optionally selects the first element.
Optionally selects the first element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
the first element of this traversable collection if it is nonempty,
None
if it is empty.
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
init: Map[K, V]
Selects all elements except the last.
Selects all elements except the last.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
a traversable collection consisting of all elements of this traversable collection except the last one.
- Definition Classes
- TraversableLike → GenTraversableLike
- Exceptions thrown
UnsupportedOperationException
if the traversable collection is empty.
-
def
inits: Iterator[Map[K, V]]
Iterates over the inits of this traversable collection.
Iterates over the inits of this traversable collection. The first value will be this traversable collection and the final one will be an empty traversable collection, with the intervening values the results of successive applications of
init
.- returns
an iterator over all the inits of this traversable collection
- Definition Classes
- TraversableLike
List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)
Example: -
def
isDefinedAt(key: K): Boolean
Tests whether this map contains a binding for a key.
Tests whether this map contains a binding for a key. This method, which implements an abstract method of trait
PartialFunction
, is equivalent tocontains
.- key
the key
- returns
true
if there is a binding forkey
in this map,false
otherwise.
- Definition Classes
- MapLike → GenMapLike → PartialFunction
-
def
isEmpty: Boolean
Tests whether the map is empty.
Tests whether the map is empty.
- returns
true
if the map does not contain any key/value binding,false
otherwise.
- Definition Classes
- MapLike → IterableLike → TraversableLike → TraversableOnce → GenTraversableOnce
-
final
def
isInstanceOf[T0]: Boolean
Test whether the dynamic type of the receiver object is
T0
.Test whether the dynamic type of the receiver object is
T0
.Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression
1.isInstanceOf[String]
will returnfalse
, while the expressionList(1).isInstanceOf[List[String]]
will returntrue
. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.- returns
true
if the receiver object is an instance of erasure of typeT0
;false
otherwise.
- Definition Classes
- Any
-
final
def
isTraversableAgain: Boolean
Tests whether this traversable collection can be repeatedly traversed.
Tests whether this traversable collection can be repeatedly traversed.
- returns
true
- Definition Classes
- TraversableLike → GenTraversableLike → GenTraversableOnce
-
def
keySet: collection.Set[K]
Collects all keys of this map in a set.
Collects all keys of this map in a set.
- returns
a set containing all keys of this map.
- Definition Classes
- MapLike → GenMapLike
-
def
keys: collection.Iterable[K]
Collects all keys of this map in an iterable collection.
Collects all keys of this map in an iterable collection.
- returns
the keys of this map as an iterable.
- Definition Classes
- MapLike → GenMapLike
- Annotations
- @migration
- Migration
(Changed in version 2.8.0)
keys
returnsIterable[K]
rather thanIterator[K]
.
-
def
keysIterator: Iterator[K]
Creates an iterator for all keys.
Creates an iterator for all keys.
- returns
an iterator over all keys.
- Definition Classes
- MapLike → GenMapLike
-
def
last: (K, V)
Selects the last element.
Selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
The last element of this traversable collection.
- Definition Classes
- TraversableLike → GenTraversableLike
- Exceptions thrown
NoSuchElementException
If the traversable collection is empty.
-
def
lastOption: Option[(K, V)]
Optionally selects the last element.
Optionally selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
the last element of this traversable collection$ if it is nonempty,
None
if it is empty.
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
lift: (K) ⇒ Option[V]
Turns this partial function into a plain function returning an
Option
result.Turns this partial function into a plain function returning an
Option
result.- returns
a function that takes an argument
x
toSome(this(x))
ifthis
is defined forx
, and toNone
otherwise.
- Definition Classes
- PartialFunction
- See also
Function.unlift
-
def
map[B](f: (A) ⇒ B): Map[B]
[use case] Builds a new collection by applying a function to all elements of this mutable map.
[use case]Builds a new collection by applying a function to all elements of this mutable map.
- B
the element type of the returned collection.
- f
the function to apply to each element.
- returns
a new mutable map resulting from applying the given function
f
to each element of this mutable map and collecting the results.
- Definition Classes
- TraversableLike → GenTraversableLike → FilterMonadic
Full Signaturedef map[B, That](f: ((K, V)) ⇒ B)(implicit bf: CanBuildFrom[Map[K, V], B, That]): That
-
def
mapResult[NewTo](f: (Map[K, V]) ⇒ NewTo): Builder[(K, V), NewTo]
Creates a new builder by applying a transformation function to the results of this builder.
Creates a new builder by applying a transformation function to the results of this builder.
- NewTo
the type of collection returned by
f
.- f
the transformation function.
- returns
a new builder which is the same as the current builder except that a transformation function is applied to this builder's result.
- Definition Classes
- Builder
- Note
The original builder should no longer be used after
mapResult
is called.
-
def
mapValues[W](f: (V) ⇒ W): collection.Map[K, W]
Transforms this map by applying a function to every retrieved value.
Transforms this map by applying a function to every retrieved value.
- f
the function used to transform values of this map.
- returns
a map view which maps every key of this map to
f(this(key))
. The resulting map wraps the original map without copying any elements.
- Definition Classes
- MapLike → GenMapLike
-
def
max: A
[use case] Finds the largest element.
[use case]Finds the largest element.
- returns
the largest element of this mutable map.
- Definition Classes
- TraversableOnce → GenTraversableOnce
- Exceptions thrown
UnsupportedOperationException
if this mutable map is empty.
Full Signaturedef max[B >: (K, V)](implicit cmp: Ordering[B]): (K, V)
-
def
maxBy[B](f: (A) ⇒ B): A
[use case] Finds the first element which yields the largest value measured by function f.
[use case]Finds the first element which yields the largest value measured by function f.
- B
The result type of the function f.
- f
The measuring function.
- returns
the first element of this mutable map with the largest value measured by function f.
- Definition Classes
- TraversableOnce → GenTraversableOnce
- Exceptions thrown
UnsupportedOperationException
if this mutable map is empty.
Full Signaturedef maxBy[B](f: ((K, V)) ⇒ B)(implicit cmp: Ordering[B]): (K, V)
-
def
min: A
[use case] Finds the smallest element.
[use case]Finds the smallest element.
- returns
the smallest element of this mutable map
- Definition Classes
- TraversableOnce → GenTraversableOnce
- Exceptions thrown
UnsupportedOperationException
if this mutable map is empty.
Full Signaturedef min[B >: (K, V)](implicit cmp: Ordering[B]): (K, V)
-
def
minBy[B](f: (A) ⇒ B): A
[use case] Finds the first element which yields the smallest value measured by function f.
[use case]Finds the first element which yields the smallest value measured by function f.
- B
The result type of the function f.
- f
The measuring function.
- returns
the first element of this mutable map with the smallest value measured by function f.
- Definition Classes
- TraversableOnce → GenTraversableOnce
- Exceptions thrown
UnsupportedOperationException
if this mutable map is empty.
Full Signaturedef minBy[B](f: ((K, V)) ⇒ B)(implicit cmp: Ordering[B]): (K, V)
-
def
mkString: String
Displays all elements of this traversable or iterator in a string.
Displays all elements of this traversable or iterator in a string.
- returns
a string representation of this traversable or iterator. In the resulting string the string representations (w.r.t. the method
toString
) of all elements of this traversable or iterator follow each other without any separator string.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
mkString(sep: String): String
Displays all elements of this traversable or iterator in a string using a separator string.
Displays all elements of this traversable or iterator in a string using a separator string.
- sep
the separator string.
- returns
a string representation of this traversable or iterator. In the resulting string the string representations (w.r.t. the method
toString
) of all elements of this traversable or iterator are separated by the stringsep
.
- Definition Classes
- TraversableOnce → GenTraversableOnce
List(1, 2, 3).mkString("|") = "1|2|3"
Example: -
def
mkString(start: String, sep: String, end: String): String
Displays all elements of this traversable or iterator in a string using start, end, and separator strings.
Displays all elements of this traversable or iterator in a string using start, end, and separator strings.
- start
the starting string.
- sep
the separator string.
- end
the ending string.
- returns
a string representation of this traversable or iterator. The resulting string begins with the string
start
and ends with the stringend
. Inside, the string representations (w.r.t. the methodtoString
) of all elements of this traversable or iterator are separated by the stringsep
.
- Definition Classes
- TraversableOnce → GenTraversableOnce
List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
Example: -
final
def
ne(arg0: AnyRef): Boolean
Equivalent to
!(this eq that)
.Equivalent to
!(this eq that)
.- returns
true
if the argument is not a reference to the receiver object;false
otherwise.
- Definition Classes
- AnyRef
-
def
newBuilder: Builder[(K, V), Map[K, V]]
A common implementation of
newBuilder
for all mutable maps in terms ofempty
.A common implementation of
newBuilder
for all mutable maps in terms ofempty
.Overrides
MapLike
implementation for better efficiency.- Attributes
- protected[this]
- Definition Classes
- MapLike → MapLike → TraversableLike → HasNewBuilder
-
def
nonEmpty: Boolean
Tests whether the traversable or iterator is not empty.
Tests whether the traversable or iterator is not empty.
- returns
true
if the traversable or iterator contains at least one element,false
otherwise.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
final
def
notify(): Unit
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up a single thread that is waiting on the receiver object's monitor.
- Definition Classes
- AnyRef
- Annotations
- @native()
- Note
not specified by SLS as a member of AnyRef
-
final
def
notifyAll(): Unit
Wakes up all threads that are waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.
- Definition Classes
- AnyRef
- Annotations
- @native()
- Note
not specified by SLS as a member of AnyRef
-
def
orElse[A1 <: K, B1 >: V](that: PartialFunction[A1, B1]): PartialFunction[A1, B1]
Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.
Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.
- A1
the argument type of the fallback function
- B1
the result type of the fallback function
- that
the fallback function
- returns
a partial function which has as domain the union of the domains of this partial function and
that
. The resulting partial function takesx
tothis(x)
wherethis
is defined, and tothat(x)
where it is not.
- Definition Classes
- PartialFunction
-
def
par: ParMap[K, V]
Returns a parallel implementation of this collection.
Returns a parallel implementation of this collection.
For most collection types, this method creates a new parallel collection by copying all the elements. For these collection,
par
takes linear time. Mutable collections in this category do not produce a mutable parallel collection that has the same underlying dataset, so changes in one collection will not be reflected in the other one.Specific collections (e.g.
ParArray
ormutable.ParHashMap
) override this default behaviour by creating a parallel collection which shares the same underlying dataset. For these collections,par
takes constant or sublinear time.All parallel collections return a reference to themselves.
- returns
a parallel implementation of this collection
- Definition Classes
- Parallelizable
-
def
parCombiner: Combiner[(K, V), ParMap[K, V]]
The default
par
implementation uses the combiner provided by this method to create a new parallel collection.The default
par
implementation uses the combiner provided by this method to create a new parallel collection.- returns
a combiner for the parallel collection of type
ParRepr
- Attributes
- protected[this]
- Definition Classes
- MapLike → MapLike → TraversableLike → Parallelizable
-
def
partition(p: ((K, V)) ⇒ Boolean): (Map[K, V], Map[K, V])
Partitions this traversable collection in two traversable collections according to a predicate.
Partitions this traversable collection in two traversable collections according to a predicate.
- p
the predicate on which to partition.
- returns
a pair of traversable collections: the first traversable collection consists of all elements that satisfy the predicate
p
and the second traversable collection consists of all elements that don't. The relative order of the elements in the resulting traversable collections is the same as in the original traversable collection.
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
product: A
[use case] Multiplies up the elements of this collection.
[use case]Multiplies up the elements of this collection.
- returns
the product of all elements in this mutable map of numbers of type
Int
. Instead ofInt
, any other typeT
with an implicitNumeric[T]
implementation can be used as element type of the mutable map and as result type ofproduct
. Examples of such types are:Long
,Float
,Double
,BigInt
.
- Definition Classes
- TraversableOnce → GenTraversableOnce
Full Signaturedef product[B >: (K, V)](implicit num: Numeric[B]): B
-
def
put(key: K, value: V): Option[V]
Adds a new key/value pair to this map and optionally returns previously bound value.
Adds a new key/value pair to this map and optionally returns previously bound value. If the map already contains a mapping for the key, it will be overridden by the new value.
- key
the key to update
- value
the new value
- returns
an option value containing the value associated with the key before the
put
operation was executed, orNone
ifkey
was not defined in the map before.
- Definition Classes
- MapLike
-
def
reduce[A1 >: (K, V)](op: (A1, A1) ⇒ A1): A1
Reduces the elements of this traversable or iterator using the specified associative binary operator.
Reduces the elements of this traversable or iterator using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
- A1
A type parameter for the binary operator, a supertype of
A
.- op
A binary operator that must be associative.
- returns
The result of applying reduce operator
op
between all the elements if the traversable or iterator is nonempty.
- Definition Classes
- TraversableOnce → GenTraversableOnce
- Exceptions thrown
UnsupportedOperationException
if this traversable or iterator is empty.
-
def
reduceLeft[B >: (K, V)](op: (B, (K, V)) ⇒ B): B
Applies a binary operator to all elements of this traversable or iterator, going left to right.
Applies a binary operator to all elements of this traversable or iterator, going left to right.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
- B
the result type of the binary operator.
- op
the binary operator.
- returns
the result of inserting
op
between consecutive elements of this traversable or iterator, going left to right:op( op( ... op(x_1, x_2) ..., x_{n-1}), x_n)
where
x1, ..., xn
are the elements of this traversable or iterator.
- Definition Classes
- TraversableOnce
- Exceptions thrown
UnsupportedOperationException
if this traversable or iterator is empty.
-
def
reduceLeftOption[B >: (K, V)](op: (B, (K, V)) ⇒ B): Option[B]
Optionally applies a binary operator to all elements of this traversable or iterator, going left to right.
Optionally applies a binary operator to all elements of this traversable or iterator, going left to right.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
- B
the result type of the binary operator.
- op
the binary operator.
- returns
an option value containing the result of
reduceLeft(op)
if this traversable or iterator is nonempty,None
otherwise.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
reduceOption[A1 >: (K, V)](op: (A1, A1) ⇒ A1): Option[A1]
Reduces the elements of this traversable or iterator, if any, using the specified associative binary operator.
Reduces the elements of this traversable or iterator, if any, using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
- A1
A type parameter for the binary operator, a supertype of
A
.- op
A binary operator that must be associative.
- returns
An option value containing result of applying reduce operator
op
between all the elements if the collection is nonempty, andNone
otherwise.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
reduceRight[B >: (K, V)](op: ((K, V), B) ⇒ B): B
Applies a binary operator to all elements of this iterable collection, going right to left.
Applies a binary operator to all elements of this iterable collection, going right to left.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.
- B
the result type of the binary operator.
- op
the binary operator.
- returns
the result of inserting
op
between consecutive elements of this iterable collection, going right to left:op(x_1, op(x_2, ..., op(x_{n-1}, x_n)...))
where
x1, ..., xn
are the elements of this iterable collection.
- Definition Classes
- IterableLike → TraversableOnce → GenTraversableOnce
- Exceptions thrown
UnsupportedOperationException
if this iterable collection is empty.
-
def
reduceRightOption[B >: (K, V)](op: ((K, V), B) ⇒ B): Option[B]
Optionally applies a binary operator to all elements of this traversable or iterator, going right to left.
Optionally applies a binary operator to all elements of this traversable or iterator, going right to left.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
- B
the result type of the binary operator.
- op
the binary operator.
- returns
an option value containing the result of
reduceRight(op)
if this traversable or iterator is nonempty,None
otherwise.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
remove(key: K): Option[V]
Removes a key from this map, returning the value associated previously with that key as an option.
Removes a key from this map, returning the value associated previously with that key as an option.
- key
the key to be removed
- returns
an option value containing the value associated previously with
key
, orNone
ifkey
was not defined in the map before.
- Definition Classes
- MapLike
-
def
repr: Map[K, V]
The collection of type traversable collection underlying this
TraversableLike
object.The collection of type traversable collection underlying this
TraversableLike
object. By default this is implemented as theTraversableLike
object itself, but this can be overridden.- Definition Classes
- TraversableLike → GenTraversableLike
-
def
result(): Map[K, V]
The result when this map is used as a builder
-
def
retain(p: (K, V) ⇒ Boolean): Map.this.type
Retains only those mappings for which the predicate
p
returnstrue
.Retains only those mappings for which the predicate
p
returnstrue
.- p
The test predicate
- Definition Classes
- MapLike
-
def
reversed: List[(K, V)]
- Attributes
- protected[this]
- Definition Classes
- TraversableOnce
-
def
runWith[U](action: (V) ⇒ U): (K) ⇒ Boolean
Composes this partial function with an action function which gets applied to results of this partial function.
Composes this partial function with an action function which gets applied to results of this partial function. The action function is invoked only for its side effects; its result is ignored.
Note that expression
pf.runWith(action)(x)
is equivalent toif(pf isDefinedAt x) { action(pf(x)); true } else false
except that
runWith
is implemented viaapplyOrElse
and thus potentially more efficient. UsingrunWith
avoids double evaluation of pattern matchers and guards for partial function literals.- action
the action function
- returns
a function which maps arguments
x
toisDefinedAt(x)
. The resulting function runsaction(this(x))
wherethis
is defined.
- Definition Classes
- PartialFunction
- Since
2.10
- See also
applyOrElse
.
-
def
sameElements(that: GenIterable[A]): Boolean
[use case] Checks if the other iterable collection contains the same elements in the same order as this mutable map.
[use case]Checks if the other iterable collection contains the same elements in the same order as this mutable map.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- that
the collection to compare with.
- returns
true
, if both collections contain the same elements in the same order,false
otherwise.
- Definition Classes
- IterableLike → GenIterableLike
Full Signaturedef sameElements[B >: (K, V)](that: GenIterable[B]): Boolean
-
def
scan[B >: (K, V), That](z: B)(op: (B, B) ⇒ B)(implicit cbf: CanBuildFrom[Map[K, V], B, That]): That
Computes a prefix scan of the elements of the collection.
Computes a prefix scan of the elements of the collection.
Note: The neutral element
z
may be applied more than once.- B
element type of the resulting collection
- That
type of the resulting collection
- z
neutral element for the operator
op
- op
the associative operator for the scan
- cbf
combiner factory which provides a combiner
- returns
a new traversable collection containing the prefix scan of the elements in this traversable collection
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
scanLeft[B, That](z: B)(op: (B, (K, V)) ⇒ B)(implicit bf: CanBuildFrom[Map[K, V], B, That]): That
Produces a collection containing cumulative results of applying the operator going left to right.
Produces a collection containing cumulative results of applying the operator going left to right.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- B
the type of the elements in the resulting collection
- That
the actual type of the resulting collection
- z
the initial value
- op
the binary operator applied to the intermediate result and the element
- bf
an implicit value of class
CanBuildFrom
which determines the result classThat
from the current representation typeRepr
and the new element typeB
.- returns
collection with intermediate results
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
scanRight[B, That](z: B)(op: ((K, V), B) ⇒ B)(implicit bf: CanBuildFrom[Map[K, V], B, That]): That
Produces a collection containing cumulative results of applying the operator going right to left.
Produces a collection containing cumulative results of applying the operator going right to left. The head of the collection is the last cumulative result.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
Example:
List(1, 2, 3, 4).scanRight(0)(_ + _) == List(10, 9, 7, 4, 0)
- B
the type of the elements in the resulting collection
- That
the actual type of the resulting collection
- z
the initial value
- op
the binary operator applied to the intermediate result and the element
- bf
an implicit value of class
CanBuildFrom
which determines the result classThat
from the current representation typeRepr
and the new element typeB
.- returns
collection with intermediate results
- Definition Classes
- TraversableLike → GenTraversableLike
- Annotations
- @migration
- Migration
(Changed in version 2.9.0) The behavior of
scanRight
has changed. The previous behavior can be reproduced with scanRight.reverse.
-
def
seq: Map[K, V]
A version of this collection with all of the operations implemented sequentially (i.e., in a single-threaded manner).
A version of this collection with all of the operations implemented sequentially (i.e., in a single-threaded manner).
This method returns a reference to this collection. In parallel collections, it is redefined to return a sequential implementation of this collection. In both cases, it has O(1) complexity.
- returns
a sequential view of the collection.
- Definition Classes
- Map → Map → GenMap → GenMapLike → Iterable → Iterable → GenIterable → Traversable → Traversable → GenTraversable → Parallelizable → TraversableOnce → GenTraversableOnce
-
def
size: Int
The size of this traversable or iterator.
The size of this traversable or iterator.
Note: will not terminate for infinite-sized collections.
- returns
the number of elements in this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
sizeHint(coll: TraversableLike[_, _], delta: Int): Unit
Gives a hint that one expects the
result
of this builder to have the same size as the given collection, plus some delta.Gives a hint that one expects the
result
of this builder to have the same size as the given collection, plus some delta. This will provide a hint only if the collection is known to have a cheapsize
method. Currently this is assumed to be the case if and only if the collection is of typeIndexedSeqLike
. Some builder classes will optimize their representation based on the hint. However, builder implementations are still required to work correctly even if the hint is wrong, i.e. a different number of elements is added.- coll
the collection which serves as a hint for the result's size.
- delta
a correction to add to the
coll.size
to produce the size hint.
- Definition Classes
- Builder
-
def
sizeHint(coll: TraversableLike[_, _]): Unit
Gives a hint that one expects the
result
of this builder to have the same size as the given collection, plus some delta.Gives a hint that one expects the
result
of this builder to have the same size as the given collection, plus some delta. This will provide a hint only if the collection is known to have a cheapsize
method, which is determined by callingsizeHint
.Some builder classes will optimize their representation based on the hint. However, builder implementations are still required to work correctly even if the hint is wrong, i.e. a different number of elements is added.
- coll
the collection which serves as a hint for the result's size.
- Definition Classes
- Builder
-
def
sizeHint(size: Int): Unit
Gives a hint how many elements are expected to be added when the next
result
is called.Gives a hint how many elements are expected to be added when the next
result
is called. Some builder classes will optimize their representation based on the hint. However, builder implementations are still required to work correctly even if the hint is wrong, i.e. a different number of elements is added.- size
the hint how many elements will be added.
- Definition Classes
- Builder
-
def
sizeHintBounded(size: Int, boundingColl: TraversableLike[_, _]): Unit
Gives a hint how many elements are expected to be added when the next
result
is called, together with an upper bound given by the size of some other collection.Gives a hint how many elements are expected to be added when the next
result
is called, together with an upper bound given by the size of some other collection. Some builder classes will optimize their representation based on the hint. However, builder implementations are still required to work correctly even if the hint is wrong, i.e. a different number of elements is added.- size
the hint how many elements will be added.
- boundingColl
the bounding collection. If it is an IndexedSeqLike, then sizes larger than collection's size are reduced.
- Definition Classes
- Builder
-
def
sizeHintIfCheap: Int
The size of this collection or iterator, if it can be cheaply computed
The size of this collection or iterator, if it can be cheaply computed
- returns
the number of elements in this collection or iterator, or -1 if the size cannot be determined cheaply
- Attributes
- protected[collection]
- Definition Classes
- GenTraversableOnce
-
def
slice(from: Int, until: Int): Map[K, V]
Selects an interval of elements.
Selects an interval of elements. The returned collection is made up of all elements
x
which satisfy the invariant:from <= indexOf(x) < until
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
a iterable collection containing the elements greater than or equal to index
from
extending up to (but not including) indexuntil
of this iterable collection.
- Definition Classes
- IterableLike → TraversableLike → GenTraversableLike
-
def
sliding(size: Int, step: Int): Iterator[Map[K, V]]
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)
- size
the number of elements per group
- step
the distance between the first elements of successive groups
- returns
An iterator producing iterable collections of size
size
, except the last element (which may be the only element) will be truncated if there are fewer thansize
elements remaining to be grouped.
- Definition Classes
- IterableLike
- See also
scala.collection.Iterator, method
sliding
-
def
sliding(size: Int): Iterator[Map[K, V]]
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in
grouped
.) The "sliding window" step is set to one.Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in
grouped
.) The "sliding window" step is set to one.- size
the number of elements per group
- returns
An iterator producing iterable collections of size
size
, except the last element (which may be the only element) will be truncated if there are fewer thansize
elements remaining to be grouped.
- Definition Classes
- IterableLike
- See also
scala.collection.Iterator, method
sliding
-
def
span(p: ((K, V)) ⇒ Boolean): (Map[K, V], Map[K, V])
Splits this traversable collection into a prefix/suffix pair according to a predicate.
Splits this traversable collection into a prefix/suffix pair according to a predicate.
Note:
c span p
is equivalent to (but possibly more efficient than)(c takeWhile p, c dropWhile p)
, provided the evaluation of the predicatep
does not cause any side-effects.Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
a pair consisting of the longest prefix of this traversable collection whose elements all satisfy
p
, and the rest of this traversable collection.
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
splitAt(n: Int): (Map[K, V], Map[K, V])
Splits this traversable collection into two at a given position.
Splits this traversable collection into two at a given position. Note:
c splitAt n
is equivalent to (but possibly more efficient than)(c take n, c drop n)
.Note: might return different results for different runs, unless the underlying collection type is ordered.
- n
the position at which to split.
- returns
a pair of traversable collections consisting of the first
n
elements of this traversable collection, and the other elements.
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
stringPrefix: String
Defines the prefix of this object's
toString
representation.Defines the prefix of this object's
toString
representation.- returns
a string representation which starts the result of
toString
applied to this map. Unless overridden in subclasses, the string prefix of every map is"Map"
.
- Definition Classes
- MapLike → TraversableLike → GenTraversableLike
-
def
sum: A
[use case] Sums up the elements of this collection.
[use case]Sums up the elements of this collection.
- returns
the sum of all elements in this mutable map of numbers of type
Int
. Instead ofInt
, any other typeT
with an implicitNumeric[T]
implementation can be used as element type of the mutable map and as result type ofsum
. Examples of such types are:Long
,Float
,Double
,BigInt
.
- Definition Classes
- TraversableOnce → GenTraversableOnce
Full Signaturedef sum[B >: (K, V)](implicit num: Numeric[B]): B
-
final
def
synchronized[T0](arg0: ⇒ T0): T0
- Definition Classes
- AnyRef
-
def
tail: Map[K, V]
Selects all elements except the first.
Selects all elements except the first.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
a traversable collection consisting of all elements of this traversable collection except the first one.
- Definition Classes
- TraversableLike → GenTraversableLike
- Exceptions thrown
java.lang.UnsupportedOperationException
if the traversable collection is empty.
-
def
tails: Iterator[Map[K, V]]
Iterates over the tails of this traversable collection.
Iterates over the tails of this traversable collection. The first value will be this traversable collection and the final one will be an empty traversable collection, with the intervening values the results of successive applications of
tail
.- returns
an iterator over all the tails of this traversable collection
- Definition Classes
- TraversableLike
List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)
Example: -
def
take(n: Int): Map[K, V]
Selects first n elements.
Selects first n elements.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- n
the number of elements to take from this iterable collection.
- returns
a iterable collection consisting only of the first
n
elements of this iterable collection, or else the whole iterable collection, if it has less thann
elements. Ifn
is negative, returns an empty iterable collection.
- Definition Classes
- IterableLike → TraversableLike → GenTraversableLike
-
def
takeRight(n: Int): Map[K, V]
Selects last n elements.
Selects last n elements.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- n
the number of elements to take
- returns
a iterable collection consisting only of the last
n
elements of this iterable collection, or else the whole iterable collection, if it has less thann
elements.
- Definition Classes
- IterableLike
-
def
takeWhile(p: ((K, V)) ⇒ Boolean): Map[K, V]
Takes longest prefix of elements that satisfy a predicate.
Takes longest prefix of elements that satisfy a predicate.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
the longest prefix of this iterable collection whose elements all satisfy the predicate
p
.
- Definition Classes
- IterableLike → TraversableLike → GenTraversableLike
-
def
thisCollection: collection.Iterable[(K, V)]
The underlying collection seen as an instance of
Iterable
.The underlying collection seen as an instance of
Iterable
. By default this is implemented as the current collection object itself, but this can be overridden.- Attributes
- protected[this]
- Definition Classes
- IterableLike → TraversableLike
-
def
to[Col[_]]: Col[A]
[use case] Converts this mutable map into another by copying all elements.
[use case]Converts this mutable map into another by copying all elements.
- Col
The collection type to build.
- returns
a new collection containing all elements of this mutable map.
- Definition Classes
- TraversableLike → TraversableOnce → GenTraversableOnce
Full Signaturedef to[Col[_]](implicit cbf: CanBuildFrom[Nothing, (K, V), Col[(K, V)]]): Col[(K, V)]
-
def
toArray: Array[A]
[use case] Converts this mutable map to an array.
[use case]Converts this mutable map to an array.
- returns
an array containing all elements of this mutable map. An
ClassTag
must be available for the element type of this mutable map.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
toBuffer[E >: (K, V)]: Buffer[E]
Uses the contents of this map to create a new mutable buffer.
Uses the contents of this map to create a new mutable buffer.
- returns
a buffer containing all elements of this map.
- Definition Classes
- MapLike → TraversableOnce → GenTraversableOnce
-
def
toCollection(repr: Map[K, V]): collection.Iterable[(K, V)]
A conversion from collections of type
Repr
toIterable
objects.A conversion from collections of type
Repr
toIterable
objects. By default this is implemented as just a cast, but this can be overridden.- Attributes
- protected[this]
- Definition Classes
- IterableLike → TraversableLike
-
def
toIndexedSeq: immutable.IndexedSeq[(K, V)]
Converts this traversable or iterator to an indexed sequence.
Converts this traversable or iterator to an indexed sequence.
Note: will not terminate for infinite-sized collections.
- returns
an indexed sequence containing all elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
toIterable: collection.Iterable[(K, V)]
Returns this iterable collection as an iterable collection.
Returns this iterable collection as an iterable collection.
A new collection will not be built; lazy collections will stay lazy.
Note: will not terminate for infinite-sized collections.
- returns
an
Iterable
containing all elements of this iterable collection.
- Definition Classes
- IterableLike → TraversableOnce → GenTraversableOnce
-
def
toIterator: Iterator[(K, V)]
Returns an Iterator over the elements in this iterable collection.
Returns an Iterator over the elements in this iterable collection. Produces the same result as
iterator
.Note: will not terminate for infinite-sized collections.
- returns
an Iterator containing all elements of this iterable collection.
- Definition Classes
- IterableLike → TraversableLike → GenTraversableOnce
- Annotations
- @deprecatedOverriding( message = ... , since = "2.11.0" )
-
def
toList: List[(K, V)]
Converts this traversable or iterator to a list.
Converts this traversable or iterator to a list.
Note: will not terminate for infinite-sized collections.
- returns
a list containing all elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
toMap[T, U]: collection.Map[T, U]
[use case] Converts this mutable map to a map.
[use case]Converts this mutable map to a map. This method is unavailable unless the elements are members of Tuple2, each ((T, U)) becoming a key-value pair in the map. Duplicate keys will be overwritten by later keys: if this is an unordered collection, which key is in the resulting map is undefined.
- returns
a map of type
immutable.Map[T, U]
containing all key/value pairs of type(T, U)
of this mutable map.
- Definition Classes
- TraversableOnce → GenTraversableOnce
Full Signaturedef toMap[T, U](implicit ev: <:<[(K, V), (T, U)]): immutable.Map[T, U]
-
def
toParArray: ParArray[T]
- Implicit
- This member is added by an implicit conversion from Map[K, V] to CollectionsHaveToParArray[Map[K, V], T] performed by method CollectionsHaveToParArray in scala.collection.parallel. This conversion will take place only if an implicit value of type (Map[K, V]) ⇒ GenTraversableOnce[T] is in scope.
- Definition Classes
- CollectionsHaveToParArray
-
def
toSeq: collection.Seq[(K, V)]
Converts this mutable map to a sequence.
Converts this mutable map to a sequence.
: assumes a fastNote
size
method. Subclasses should override if this is not true.- returns
a sequence containing all elements of this mutable map.
- Definition Classes
- MapLike → MapLike → TraversableOnce → GenTraversableOnce
-
def
toSet[B >: (K, V)]: immutable.Set[B]
Converts this traversable or iterator to a set.
Converts this traversable or iterator to a set.
Note: will not terminate for infinite-sized collections.
- returns
a set containing all elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
toStream: immutable.Stream[(K, V)]
Converts this iterable collection to a stream.
Converts this iterable collection to a stream.
- returns
a stream containing all elements of this iterable collection.
- Definition Classes
- IterableLike → TraversableLike → GenTraversableOnce
-
def
toString(): String
Converts this map to a string.
Converts this map to a string.
- returns
a string representation of this collection. By default this string consists of the
stringPrefix
of this map, followed by all elements separated by commas and enclosed in parentheses.
- Definition Classes
- MapLike → TraversableLike → Function1 → AnyRef → Any
-
def
toTraversable: collection.Traversable[(K, V)]
Converts this traversable collection to an unspecified Traversable.
Converts this traversable collection to an unspecified Traversable. Will return the same collection if this instance is already Traversable.
Note: will not terminate for infinite-sized collections.
- returns
a Traversable containing all elements of this traversable collection.
- Definition Classes
- TraversableLike → TraversableOnce → GenTraversableOnce
- Annotations
- @deprecatedOverriding( message = ... , since = "2.11.0" )
-
def
toVector: Vector[(K, V)]
Converts this traversable or iterator to a Vector.
Converts this traversable or iterator to a Vector.
Note: will not terminate for infinite-sized collections.
- returns
a vector containing all elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
transform(f: (K, V) ⇒ V): Map.this.type
Applies a transformation function to all values contained in this map.
Applies a transformation function to all values contained in this map. The transformation function produces new values from existing keys associated values.
- f
the transformation to apply
- returns
the map itself.
- Definition Classes
- MapLike
-
def
transpose[B](implicit asTraversable: ((K, V)) ⇒ GenTraversableOnce[B]): Iterable[Iterable[B]]
Transposes this collection of traversable collections into a collection of collections.
Transposes this collection of traversable collections into a collection of collections.
The resulting collection's type will be guided by the static type of collection. For example:
val xs = List( Set(1, 2, 3), Set(4, 5, 6)).transpose // xs == List( // List(1, 4), // List(2, 5), // List(3, 6)) val ys = Vector( List(1, 2, 3), List(4, 5, 6)).transpose // ys == Vector( // Vector(1, 4), // Vector(2, 5), // Vector(3, 6))
- B
the type of the elements of each traversable collection.
- asTraversable
an implicit conversion which asserts that the element type of this collection is a
Traversable
.- returns
a two-dimensional collection of collections which has as nth row the nth column of this collection.
- Definition Classes
- GenericTraversableTemplate
- Annotations
- @migration
- Migration
(Changed in version 2.9.0)
transpose
throws anIllegalArgumentException
if collections are not uniformly sized.- Exceptions thrown
IllegalArgumentException
if all collections in this collection are not of the same size.
-
def
unzip[A1, A2](implicit asPair: ((K, V)) ⇒ (A1, A2)): (Iterable[A1], Iterable[A2])
Converts this collection of pairs into two collections of the first and second half of each pair.
Converts this collection of pairs into two collections of the first and second half of each pair.
val xs = Traversable( (1, "one"), (2, "two"), (3, "three")).unzip // xs == (Traversable(1, 2, 3), // Traversable(one, two, three))
- A1
the type of the first half of the element pairs
- A2
the type of the second half of the element pairs
- asPair
an implicit conversion which asserts that the element type of this collection is a pair.
- returns
a pair of collections, containing the first, respectively second half of each element pair of this collection.
- Definition Classes
- GenericTraversableTemplate
-
def
unzip3[A1, A2, A3](implicit asTriple: ((K, V)) ⇒ (A1, A2, A3)): (Iterable[A1], Iterable[A2], Iterable[A3])
Converts this collection of triples into three collections of the first, second, and third element of each triple.
Converts this collection of triples into three collections of the first, second, and third element of each triple.
val xs = Traversable( (1, "one", '1'), (2, "two", '2'), (3, "three", '3')).unzip3 // xs == (Traversable(1, 2, 3), // Traversable(one, two, three), // Traversable(1, 2, 3))
- A1
the type of the first member of the element triples
- A2
the type of the second member of the element triples
- A3
the type of the third member of the element triples
- asTriple
an implicit conversion which asserts that the element type of this collection is a triple.
- returns
a triple of collections, containing the first, second, respectively third member of each element triple of this collection.
- Definition Classes
- GenericTraversableTemplate
-
def
update(key: K, value: V): Unit
Adds a new key/value pair to this map.
Adds a new key/value pair to this map. If the map already contains a mapping for the key, it will be overridden by the new value.
- key
The key to update
- value
The new value
- Definition Classes
- MapLike
-
def
updated[V1 >: V](key: K, value: V1): Map[K, V1]
Creates a new map consisting of all key/value pairs of the current map plus a new pair of a given key and value.
-
def
values: collection.Iterable[V]
Collects all values of this map in an iterable collection.
Collects all values of this map in an iterable collection.
- returns
the values of this map as an iterable.
- Definition Classes
- MapLike → GenMapLike
- Annotations
- @migration
- Migration
(Changed in version 2.8.0)
values
returnsIterable[V]
rather thanIterator[V]
.
-
def
valuesIterator: Iterator[V]
Creates an iterator for all values in this map.
Creates an iterator for all values in this map.
- returns
an iterator over all values that are associated with some key in this map.
- Definition Classes
- MapLike → GenMapLike
-
def
view(from: Int, until: Int): IterableView[(K, V), Map[K, V]]
Creates a non-strict view of a slice of this iterable collection.
Creates a non-strict view of a slice of this iterable collection.
Note: the difference between
view
andslice
is thatview
produces a view of the current iterable collection, whereasslice
produces a new iterable collection.Note:
view(from, to)
is equivalent toview.slice(from, to)
Note: might return different results for different runs, unless the underlying collection type is ordered.
- from
the index of the first element of the view
- until
the index of the element following the view
- returns
a non-strict view of a slice of this iterable collection, starting at index
from
and extending up to (but not including) indexuntil
.
- Definition Classes
- IterableLike → TraversableLike
-
def
view: IterableView[(K, V), Map[K, V]]
Creates a non-strict view of this iterable collection.
Creates a non-strict view of this iterable collection.
- returns
a non-strict view of this iterable collection.
- Definition Classes
- IterableLike → TraversableLike
-
final
def
wait(): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long, arg1: Int): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
- final def wait(arg0: Long): Unit
-
def
withDefault(d: (K) ⇒ V): Map[K, V]
The same map with a given default function.
The same map with a given default function.
Invoking transformer methods (e.g.
map
) will not preserve the default value.- d
the function mapping keys to values, used for non-present keys
- returns
a wrapper of the map with a default value
-
def
withDefaultValue(d: V): Map[K, V]
The same map with a given default value.
The same map with a given default value.
Invoking transformer methods (e.g.
map
) will not preserve the default value.- d
default value used for non-present keys
- returns
a wrapper of the map with a default value
-
def
withFilter(p: ((K, V)) ⇒ Boolean): FilterMonadic[(K, V), Map[K, V]]
Creates a non-strict filter of this traversable collection.
Creates a non-strict filter of this traversable collection.
Note: the difference between
c filter p
andc withFilter p
is that the former creates a new collection, whereas the latter only restricts the domain of subsequentmap
,flatMap
,foreach
, andwithFilter
operations.Note: might return different results for different runs, unless the underlying collection type is ordered.
- p
the predicate used to test elements.
- returns
an object of class
WithFilter
, which supportsmap
,flatMap
,foreach
, andwithFilter
operations. All these operations apply to those elements of this traversable collection which satisfy the predicatep
.
- Definition Classes
- TraversableLike → FilterMonadic
-
def
zip[B](that: GenIterable[B]): Map[(A, B)]
[use case] Returns a mutable map formed from this mutable map and another iterable collection by combining corresponding elements in pairs.
[use case]Returns a mutable map formed from this mutable map and another iterable collection by combining corresponding elements in pairs. If one of the two collections is longer than the other, its remaining elements are ignored.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- B
the type of the second half of the returned pairs
- that
The iterable providing the second half of each result pair
- returns
a new mutable map containing pairs consisting of corresponding elements of this mutable map and
that
. The length of the returned collection is the minimum of the lengths of this mutable map andthat
.
- Definition Classes
- IterableLike → GenIterableLike
Full Signaturedef zip[A1 >: (K, V), B, That](that: GenIterable[B])(implicit bf: CanBuildFrom[Map[K, V], (A1, B), That]): That
-
def
zipAll[B](that: collection.Iterable[B], thisElem: A, thatElem: B): Map[(A, B)]
[use case] Returns a mutable map formed from this mutable map and another iterable collection by combining corresponding elements in pairs.
[use case]Returns a mutable map formed from this mutable map and another iterable collection by combining corresponding elements in pairs. If one of the two collections is shorter than the other, placeholder elements are used to extend the shorter collection to the length of the longer.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- B
the type of the second half of the returned pairs
- that
The iterable providing the second half of each result pair
- thisElem
the element to be used to fill up the result if this mutable map is shorter than
that
.- thatElem
the element to be used to fill up the result if
that
is shorter than this mutable map.- returns
a new mutable map containing pairs consisting of corresponding elements of this mutable map and
that
. The length of the returned collection is the maximum of the lengths of this mutable map andthat
. If this mutable map is shorter thanthat
,thisElem
values are used to pad the result. Ifthat
is shorter than this mutable map,thatElem
values are used to pad the result.
- Definition Classes
- IterableLike → GenIterableLike
Full Signaturedef zipAll[B, A1 >: (K, V), That](that: GenIterable[B], thisElem: A1, thatElem: B)(implicit bf: CanBuildFrom[Map[K, V], (A1, B), That]): That
-
def
zipWithIndex: Map[(A, Int)]
[use case] Zips this mutable map with its indices.
[use case]Zips this mutable map with its indices.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
A new mutable map containing pairs consisting of all elements of this mutable map paired with their index. Indices start at
0
.
- Definition Classes
- IterableLike → GenIterableLike
List("a", "b", "c").zipWithIndex = List(("a", 0), ("b", 1), ("c", 2))
Full Signaturedef zipWithIndex[A1 >: (K, V), That](implicit bf: CanBuildFrom[Map[K, V], (A1, Int), That]): That
Example: -
def
→[B](y: B): (Map[K, V], B)
- Implicit
- This member is added by an implicit conversion from Map[K, V] to ArrowAssoc[Map[K, V]] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
Shadowed Implicit Value Members
-
def
+(other: String): String
- Implicit
- This member is added by an implicit conversion from Map[K, V] to any2stringadd[Map[K, V]] performed by method any2stringadd in scala.Predef.
- Shadowing
- This implicitly inherited member is shadowed by one or more members in this class.
To access this member you can use a type ascription:(map: any2stringadd[Map[K, V]]).+(other)
- Definition Classes
- any2stringadd
-
def
filter(p: ((K, V)) ⇒ Boolean): TraversableOnce[(K, V)]
- Implicit
- This member is added by an implicit conversion from Map[K, V] to MonadOps[(K, V)] performed by method MonadOps in scala.collection.TraversableOnce.
- Shadowing
- This implicitly inherited member is shadowed by one or more members in this class.
To access this member you can use a type ascription:(map: MonadOps[(K, V)]).filter(p)
- Definition Classes
- MonadOps
-
def
flatMap[B](f: ((K, V)) ⇒ GenTraversableOnce[B]): TraversableOnce[B]
- Implicit
- This member is added by an implicit conversion from Map[K, V] to MonadOps[(K, V)] performed by method MonadOps in scala.collection.TraversableOnce.
- Shadowing
- This implicitly inherited member is shadowed by one or more members in this class.
To access this member you can use a type ascription:(map: MonadOps[(K, V)]).flatMap(f)
- Definition Classes
- MonadOps
-
def
map[B](f: ((K, V)) ⇒ B): TraversableOnce[B]
- Implicit
- This member is added by an implicit conversion from Map[K, V] to MonadOps[(K, V)] performed by method MonadOps in scala.collection.TraversableOnce.
- Shadowing
- This implicitly inherited member is shadowed by one or more members in this class.
To access this member you can use a type ascription:(map: MonadOps[(K, V)]).map(f)
- Definition Classes
- MonadOps
-
def
withFilter(p: ((K, V)) ⇒ Boolean): Iterator[(K, V)]
- Implicit
- This member is added by an implicit conversion from Map[K, V] to MonadOps[(K, V)] performed by method MonadOps in scala.collection.TraversableOnce.
- Shadowing
- This implicitly inherited member is shadowed by one or more members in this class.
To access this member you can use a type ascription:(map: MonadOps[(K, V)]).withFilter(p)
- Definition Classes
- MonadOps
Deprecated Value Members
-
def
/:[B](z: B)(op: (B, (K, V)) ⇒ B): B
Applies a binary operator to a start value and all elements of this traversable or iterator, going left to right.
Applies a binary operator to a start value and all elements of this traversable or iterator, going left to right.
Note:
/:
is alternate syntax forfoldLeft
;z /: xs
is the same asxs foldLeft z
.Examples:
Note that the folding function used to compute b is equivalent to that used to compute c.
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = (5 /: a)(_+_) b: Int = 15 scala> val c = (5 /: a)((x,y) => x + y) c: Int = 15
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
- B
the result type of the binary operator.
- z
the start value.
- op
the binary operator.
- returns
the result of inserting
op
between consecutive elements of this traversable or iterator, going left to right with the start valuez
on the left:op(...op(op(z, x_1), x_2), ..., x_n)
where
x1, ..., xn
are the elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
- Annotations
- @deprecated
- Deprecated
(Since version 2.12.10) Use foldLeft instead of /:
-
def
:\[B](z: B)(op: ((K, V), B) ⇒ B): B
Applies a binary operator to all elements of this traversable or iterator and a start value, going right to left.
Applies a binary operator to all elements of this traversable or iterator and a start value, going right to left.
Note:
:\
is alternate syntax forfoldRight
;xs :\ z
is the same asxs foldRight z
.Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
Examples:
Note that the folding function used to compute b is equivalent to that used to compute c.
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = (a :\ 5)(_+_) b: Int = 15 scala> val c = (a :\ 5)((x,y) => x + y) c: Int = 15
- B
the result type of the binary operator.
- z
the start value
- op
the binary operator
- returns
the result of inserting
op
between consecutive elements of this traversable or iterator, going right to left with the start valuez
on the right:op(x_1, op(x_2, ... op(x_n, z)...))
where
x1, ..., xn
are the elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
- Annotations
- @deprecated
- Deprecated
(Since version 2.12.10) Use foldRight instead of :\
-
def
formatted(fmtstr: String): String
Returns string formatted according to given
format
string.Returns string formatted according to given
format
string. Format strings are as forString.format
(@see java.lang.String.format).- Implicit
- This member is added by an implicit conversion from Map[K, V] to StringFormat[Map[K, V]] performed by method StringFormat in scala.Predef.
- Definition Classes
- StringFormat
- Annotations
- @deprecated @inline()
- Deprecated
(Since version 2.12.16) Use
formatString.format(value)
instead ofvalue.formatted(formatString)
, or use thef""
string interpolator. In Java 15 and later,formatted
resolves to the new method in String which has reversed parameters.
This is the documentation for the Scala standard library.
Package structure
The scala package contains core types like
Int
,Float
,Array
orOption
which are accessible in all Scala compilation units without explicit qualification or imports.Notable packages include:
scala.collection
and its sub-packages contain Scala's collections frameworkscala.collection.immutable
- Immutable, sequential data-structures such asVector
,List
,Range
,HashMap
orHashSet
scala.collection.mutable
- Mutable, sequential data-structures such asArrayBuffer
,StringBuilder
,HashMap
orHashSet
scala.collection.concurrent
- Mutable, concurrent data-structures such asTrieMap
scala.collection.parallel.immutable
- Immutable, parallel data-structures such asParVector
,ParRange
,ParHashMap
orParHashSet
scala.collection.parallel.mutable
- Mutable, parallel data-structures such asParArray
,ParHashMap
,ParTrieMap
orParHashSet
scala.concurrent
- Primitives for concurrent programming such asFutures
andPromises
scala.io
- Input and output operationsscala.math
- Basic math functions and additional numeric types likeBigInt
andBigDecimal
scala.sys
- Interaction with other processes and the operating systemscala.util.matching
- Regular expressionsOther packages exist. See the complete list on the right.
Additional parts of the standard library are shipped as separate libraries. These include:
scala.reflect
- Scala's reflection API (scala-reflect.jar)scala.xml
- XML parsing, manipulation, and serialization (scala-xml.jar)scala.swing
- A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)scala.util.parsing
- Parser combinators (scala-parser-combinators.jar)Automatic imports
Identifiers in the scala package and the
scala.Predef
object are always in scope by default.Some of these identifiers are type aliases provided as shortcuts to commonly used classes. For example,
List
is an alias forscala.collection.immutable.List
.Other aliases refer to classes provided by the underlying platform. For example, on the JVM,
String
is an alias forjava.lang.String
.