Packages

  • package root

    This is the documentation for the Scala standard library.

    This is the documentation for the Scala standard library.

    Package structure

    The scala package contains core types like Int, Float, Array or Option which are accessible in all Scala compilation units without explicit qualification or imports.

    Notable packages include:

    Other packages exist. See the complete list on the right.

    Additional parts of the standard library are shipped as separate libraries. These include:

    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 for scala.collection.immutable.List.

    Other aliases refer to classes provided by the underlying platform. For example, on the JVM, String is an alias for java.lang.String.

    Definition Classes
    root
  • package scala

    Core Scala types.

    Core Scala types. They are always available without an explicit import.

    Definition Classes
    root
  • package util
    Definition Classes
    scala
  • sealed abstract class Try[+T] extends Product with Serializable

    The Try type represents a computation that may fail during evaluation by raising an exception.

    The Try type represents a computation that may fail during evaluation by raising an exception. It holds either a successfully computed value or the exception that was thrown. This is similar to the scala.util.Either type, but with different semantics.

    Instances of Try[T] are an instance of either scala.util.Success[T] or scala.util.Failure[T].

    For example, consider a computation that performs division on user-defined input. Try can reduce or eliminate the need for explicit exception handling in all of the places where an exception might be thrown.

    Example:

    import scala.io.StdIn
    import scala.util.{Try, Success, Failure}
    
    def divide: Try[Int] = {
      val dividend = Try(StdIn.readLine("Enter an Int that you'd like to divide:\n").toInt)
      val divisor = Try(StdIn.readLine("Enter an Int that you'd like to divide by:\n").toInt)
      val problem = dividend.flatMap(x => divisor.map(y => x/y))
      problem match {
        case Success(v) =>
          println("Result of " + dividend.get + "/"+ divisor.get +" is: " + v)
          Success(v)
        case Failure(e) =>
          println("You must've divided by zero or entered something that's not an Int. Try again!")
          println("Info from the exception: " + e.getMessage)
          divide
      }
    }

    An important property of Try shown in the above example is its ability to pipeline, or chain, operations, catching exceptions along the way. The flatMap and map combinators in the above example each essentially pass off either their successfully completed value, wrapped in the Success type for it to be further operated upon by the next combinator in the chain, or the exception wrapped in the Failure type usually to be simply passed on down the chain. Combinators such as recover and recoverWith are designed to provide some type of default behavior in the case of failure.

    Note: only non-fatal exceptions are caught by the combinators on Try (see scala.util.control.NonFatal). Serious system errors, on the other hand, will be thrown.

    Note:: all Try combinators will catch exceptions and return failure unless otherwise specified in the documentation.

    Definition Classes
    util
  • WithFilter
c

scala.util.Try

WithFilter

final class WithFilter extends AnyRef

We need a whole WithFilter class to honor the "doesn't create a new collection" contract even though it seems unlikely to matter much in a collection with max size 1.

Source
Try.scala
Linear Supertypes
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  2. By Inheritance
Inherited
  1. WithFilter
  2. AnyRef
  3. Any
Implicitly
  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. by ArrowAssoc
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Visibility
  1. Public
  2. Protected

Instance Constructors

  1. new WithFilter(p: (T) => Boolean)

Value Members

  1. 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
  2. final def ##: Int

    Equivalent to x.hashCode except for boxed numeric types and null.

    Equivalent to x.hashCode except for boxed numeric types and null. 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. For null returns a hashcode where null.hashCode throws a NullPointerException.

    returns

    a hash value consistent with ==

    Definition Classes
    AnyRef → Any
  3. def +(other: String): String
    Implicit
    This member is added by an implicit conversion from WithFilter toany2stringadd[WithFilter] performed by method any2stringadd in scala.Predef.
    Definition Classes
    any2stringadd
  4. def ->[B](y: B): (WithFilter, B)
    Implicit
    This member is added by an implicit conversion from WithFilter toArrowAssoc[WithFilter] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()
  5. final def ==(arg0: Any): Boolean

    The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

    The expression x == that is equivalent to if (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
  6. 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 of T0, 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 when T0 is a primitive type. When T0 is primitive, asInstanceOf may insert a conversion instead of a type test. If your intent is to convert, use a toT 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 of T0, if that can be checked on this platform

  7. 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.

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.CloneNotSupportedException]) @native()
    Note

    not specified by SLS as a member of AnyRef

  8. def ensuring(cond: (WithFilter) => Boolean, msg: => Any): WithFilter
    Implicit
    This member is added by an implicit conversion from WithFilter toEnsuring[WithFilter] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  9. def ensuring(cond: (WithFilter) => Boolean): WithFilter
    Implicit
    This member is added by an implicit conversion from WithFilter toEnsuring[WithFilter] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  10. def ensuring(cond: Boolean, msg: => Any): WithFilter
    Implicit
    This member is added by an implicit conversion from WithFilter toEnsuring[WithFilter] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  11. def ensuring(cond: Boolean): WithFilter
    Implicit
    This member is added by an implicit conversion from WithFilter toEnsuring[WithFilter] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  12. 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 of AnyRef, and has three additional properties:

    • It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
    • For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
    • null.eq(null) returns true.

    When overriding the equals or hashCode 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
  13. def equals(arg0: AnyRef): Boolean

    The equality method for reference types.

    The equality method for reference types. Default implementation delegates to eq.

    See also equals in scala.Any.

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    Definition Classes
    AnyRef → Any
  14. 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 between finalize 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

  15. def flatMap[U](f: (T) => Try[U]): Try[U]
  16. def foreach[U](f: (T) => U): Unit
  17. final def getClass(): Class[_ <: AnyRef]

    Returns the runtime class representation of the object.

    Returns the runtime class representation of the object.

    returns

    a class object corresponding to the runtime type of the receiver.

    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  18. 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
    AnyRef → Any
    Annotations
    @native()
  19. 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 returns true if the value of the receiver object is a BigDecimal or a subtype of BigDecimal.
    • T0 is a parameterized class type, e.g. List[Int]: this method returns true if the value of the receiver object is some List[X] for any X. For example, List(1, 2, 3).isInstanceOf[List[String]] will return true.
    • T0 is some singleton type x.type or literal x: this method returns this.eq(x). For example, x.isInstanceOf[1] is equivalent to x.eq(1)
    • T0 is an intersection X with Y or X & Y: this method is equivalent to x.isInstanceOf[X] && x.isInstanceOf[Y]
    • T0 is a union X | Y: this method is equivalent to x.isInstanceOf[X] || x.isInstanceOf[Y]
    • T0 is a type parameter or an abstract type member: this method is equivalent to isInstanceOf[U] where U is T0's upper bound, Any if T0 is unbounded. For example, x.isInstanceOf[A] where A is an unbounded type parameter will return true for any value of x.

    This is exactly equivalent to the type pattern _: T0

    returns

    true if the receiver object is an instance of erasure of type T0; false otherwise.

    Definition Classes
    Any
    Note

    due to the unexpectedness of List(1, 2, 3).isInstanceOf[List[String]] returning true and x.isInstanceOf[A] where A is a type parameter or abstract member returning true, these forms issue a warning.

  20. def map[U](f: (T) => U): Try[U]
  21. 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
  22. 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

  23. 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

  24. final def synchronized[T0](arg0: => T0): T0

    Executes the code in body with an exclusive lock on this.

    Executes the code in body with an exclusive lock on this.

    returns

    the result of body

    Definition Classes
    AnyRef
  25. 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
  26. 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

  27. 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

  28. final def wait(arg0: Long): Unit

    See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-.

    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException]) @native()
    Note

    not specified by SLS as a member of AnyRef

  29. def withFilter(q: (T) => Boolean): WithFilter

Deprecated Value Members

  1. 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 for String.format (@see java.lang.String.format).

    Implicit
    This member is added by an implicit conversion from WithFilter toStringFormat[WithFilter] performed by method StringFormat in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @deprecated @inline()
    Deprecated

    (Since version 2.12.16) Use formatString.format(value) instead of value.formatted(formatString), or use the f"" string interpolator. In Java 15 and later, formatted resolves to the new method in String which has reversed parameters.

  2. def [B](y: B): (WithFilter, B)
    Implicit
    This member is added by an implicit conversion from WithFilter toArrowAssoc[WithFilter] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @deprecated
    Deprecated

    (Since version 2.13.0) Use -> instead. If you still wish to display it as one character, consider using a font with programming ligatures such as Fira Code.

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd fromWithFilter to any2stringadd[WithFilter]

Inherited by implicit conversion StringFormat fromWithFilter to StringFormat[WithFilter]

Inherited by implicit conversion Ensuring fromWithFilter to Ensuring[WithFilter]

Inherited by implicit conversion ArrowAssoc fromWithFilter to ArrowAssoc[WithFilter]

Ungrouped