object Sorting
The Sorting
object provides convenience wrappers for java.util.Arrays.sort
.
Methods that defer to java.util.Arrays.sort
say that they do or under what
conditions that they do.
Sorting
also implements a general-purpose quicksort and stable (merge) sort
for those cases where java.util.Arrays.sort
could only be used at the cost
of a large memory penalty. If performance rather than memory usage is the
primary concern, one may wish to find alternate strategies to use
java.util.Arrays.sort
directly e.g. by boxing primitives to use
a custom ordering on them.
Sorting
provides methods where you can provide a comparison function, or
can request a sort of items that are scala.math.Ordered or that
otherwise have an implicit or explicit scala.math.Ordering.
Note also that high-performance non-default sorts for numeric types are not provided. If this is required, it is advisable to investigate other libraries that cover this use case.
- Source
- Sorting.scala
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- Sorting
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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
- 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
- final def asInstanceOf[T0]: T0
Forces the compiler to treat the receiver object as having type
T0
, even though doing so may violate type safety.Forces the compiler to treat the receiver object as having type
T0
, even though doing so may violate type safety.This method is useful when you believe you have type information the compiler doesn't, and it also isn't possible to check the type at runtime. In such situations, skipping type safety is the only option.
It is platform dependent whether
asInstanceOf
has any effect at runtime. It might do a runtime type test on the erasure ofT0
, insert a conversion (such as boxing/unboxing), fill in a default value, or do nothing at all.In particular,
asInstanceOf
is not a type test. It does **not** mean:this match { case x: T0 => x case _ => throw ClassCastException("...")
Use pattern matching or isInstanceOf for type testing instead.
Situations where
asInstanceOf
is useful:- when flow analysis fails to deduce
T0
automatically - when down-casting a type parameter or an abstract type member (which cannot be checked at runtime due to type erasure) If there is any doubt and you are able to type test instead, you should do so.
Be careful of using
asInstanceOf
whenT0
is a primitive type. WhenT0
is primitive,asInstanceOf
may insert a conversion instead of a type test. If your intent is to convert, use atoT
method (x.toChar
,x.toByte
, etc.).- returns
the receiver object.
- Definition Classes
- Any
- Exceptions thrown
ClassCastException
if the receiver is not an instance of the erasure ofT0
, if that can be checked on this platform
- when flow analysis fails to deduce
- def clone(): AnyRef
Create a copy of the receiver object.
Create a copy of the receiver object.
The default implementation of the
clone
method is platform dependent.- returns
a copy of the receiver object.
- 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(arg0: AnyRef): Boolean
The equality method for reference types.
- 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
- final def getClass(): Class[_ <: AnyRef]
Returns the runtime class representation of the object.
- def hashCode(): Int
The hashCode method for reference types.
- final def isInstanceOf[T0]: Boolean
Test whether the dynamic type of the receiver object has the same erasure as
T0
.Test whether the dynamic type of the receiver object has the same erasure as
T0
.Depending on what
T0
is, the test is done in one of the below ways:T0
is a non-parameterized class type, e.g.BigDecimal
: this method returnstrue
if the value of the receiver object is aBigDecimal
or a subtype ofBigDecimal
.T0
is a parameterized class type, e.g.List[Int]
: this method returnstrue
if the value of the receiver object is someList[X]
for anyX
. For example,List(1, 2, 3).isInstanceOf[List[String]]
will return true.T0
is some singleton typex.type
or literalx
: this method returnsthis.eq(x)
. For example,x.isInstanceOf[1]
is equivalent tox.eq(1)
T0
is an intersectionX with Y
orX & Y: this method is equivalent to
x.isInstanceOf[X] && x.isInstanceOf[Y]T0
is a unionX | Y
: this method is equivalent tox.isInstanceOf[X] || x.isInstanceOf[Y]
T0
is a type parameter or an abstract type member: this method is equivalent toisInstanceOf[U]
whereU
isT0
's upper bound,Any
ifT0
is unbounded. For example,x.isInstanceOf[A]
whereA
is an unbounded type parameter will return true for any value ofx
.
This is exactly equivalent to the type pattern
_: T0
- returns
true
if the receiver object is an instance of erasure of typeT0
;false
otherwise.
- Definition Classes
- Any
- Note
due to the unexpectedness of
List(1, 2, 3).isInstanceOf[List[String]]
returning true andx.isInstanceOf[A]
whereA
is a type parameter or abstract member returning true, these forms issue a warning.
- 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
- 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 quickSort[K](a: Array[K])(implicit arg0: math.Ordering[K]): Unit
Sort array
a
with quicksort, using the Ordering on its elements.Sort array
a
with quicksort, using the Ordering on its elements. This algorithm sorts in place, so no additional memory is used aside from what might be required to box individual elements during comparison. - def quickSort(a: Array[Float]): Unit
Sort an array of Floats using
java.util.Arrays.sort
. - def quickSort(a: Array[Int]): Unit
Sort an array of Ints using
java.util.Arrays.sort
. - def quickSort(a: Array[Double]): Unit
Sort an array of Doubles using
java.util.Arrays.sort
. - def stableSort[K, M](a: collection.Seq[K], f: (K) => M)(implicit arg0: ClassTag[K], arg1: math.Ordering[M]): Array[K]
A sorted Array, given an extraction function
f
that returns an ordered key for each item in the sequencea
.A sorted Array, given an extraction function
f
that returns an ordered key for each item in the sequencea
. Usesjava.util.Arrays.sort
unlessK
is a primitive type. - def stableSort[K](a: collection.Seq[K], f: (K, K) => Boolean)(implicit arg0: ClassTag[K]): Array[K]
A sorted Array, given a function
f
that computes the less-than relation for each item in the sequencea
.A sorted Array, given a function
f
that computes the less-than relation for each item in the sequencea
. Usesjava.util.Arrays.sort
unlessK
is a primitive type. - def stableSort[K](a: collection.Seq[K])(implicit arg0: ClassTag[K], arg1: math.Ordering[K]): Array[K]
A sorted Array, using the Ordering for the elements in the sequence
a
.A sorted Array, using the Ordering for the elements in the sequence
a
. Usesjava.util.Arrays.sort
unlessK
is a primitive type. - def stableSort[K](a: Array[K], f: (K, K) => Boolean, from: Int, until: Int): Unit
Sort array
a
or a part of it using functionf
that computes the less-than relation for each element.Sort array
a
or a part of it using functionf
that computes the less-than relation for each element. Usesjava.util.Arrays.sort
unlessK
is a primitive type.- a
The array to sort
- f
A function that computes the less-than relation for each element
- from
The first index in the array to sort
- until
The last index (exclusive) in the array to sort
- def stableSort[K](a: Array[K], f: (K, K) => Boolean): Unit
Sort array
a
using functionf
that computes the less-than relation for each element.Sort array
a
using functionf
that computes the less-than relation for each element. Usesjava.util.Arrays.sort
unlessK
is a primitive type. This is the same asstableSort(a, f, 0, a.length)
.- Annotations
- @inline()
- def stableSort[K](a: Array[K], from: Int, until: Int)(implicit arg0: math.Ordering[K]): Unit
Sort array
a
or a part of it using the Ordering on its elements, preserving the original ordering where possible.Sort array
a
or a part of it using the Ordering on its elements, preserving the original ordering where possible. Usesjava.util.Arrays.sort
unlessK
is a primitive type.- a
The array to sort
- from
The first index in the array to sort
- until
The last index (exclusive) in the array to sort
- def stableSort[K](a: Array[K])(implicit arg0: math.Ordering[K]): Unit
Sort array
a
using the Ordering on its elements, preserving the original ordering where possible.Sort array
a
using the Ordering on its elements, preserving the original ordering where possible. Usesjava.util.Arrays.sort
unlessK
is a primitive type. This is the same asstableSort(a, 0, a.length)
.- Annotations
- @inline()
- final def synchronized[T0](arg0: => T0): T0
Executes the code in
body
with an exclusive lock onthis
.Executes the code in
body
with an exclusive lock onthis
.- returns
the result of
body
- Definition Classes
- AnyRef
- def toString(): String
Creates a String representation of this object.
Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.
- returns
a String representation of the object.
- Definition Classes
- AnyRef → Any
- final def wait(): Unit
See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait--.
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.InterruptedException])
- Note
not specified by SLS as a member of AnyRef
- final def wait(arg0: Long, arg1: Int): Unit
See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-int-
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.InterruptedException])
- Note
not specified by SLS as a member of AnyRef
- final def wait(arg0: Long): Unit
See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-.
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.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.collection.parallel
- Parallel collections (scala-parallel-collections.jar)scala.util.parsing
- Parser combinators (scala-parser-combinators.jar)scala.swing
- A convenient wrapper around Java's GUI framework called Swing (scala-swing.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
.