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:

    • 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 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 collection

    Contains the base traits and objects needed to use and extend Scala's collection library.

    Contains the base traits and objects needed to use and extend Scala's collection library.

    Guide

    A detailed guide for using the collections library is available at http://docs.scala-lang.org/overviews/collections/introduction.html. Developers looking to extend the collections library can find a description of its architecture at http://docs.scala-lang.org/overviews/core/architecture-of-scala-collections.html.

    Using Collections

    It is convenient to treat all collections as either a scala.collection.Traversable or scala.collection.Iterable, as these traits define the vast majority of operations on a collection.

    Collections can, of course, be treated as specifically as needed, and the library is designed to ensure that the methods that transform collections will return a collection of the same type: 

    scala> val array = Array(1,2,3,4,5,6)
array: Array[Int] = Array(1, 2, 3, 4, 5, 6)

scala> array map { _.toString }
res0: Array[String] = Array(1, 2, 3, 4, 5, 6)

scala> val list = List(1,2,3,4,5,6)
list: List[Int] = List(1, 2, 3, 4, 5, 6)

scala> list map { _.toString }
res1: List[String] = List(1, 2, 3, 4, 5, 6)

    Creating Collections

    The most common way to create a collection is to use its companion object as a factory. The three most commonly used collections are scala.collection.Seq, scala.collection.immutable.Set, and scala.collection.immutable.Map. They can be used directly as shown below since their companion objects are all available as type aliases in either the scala package or in scala.Predef. New collections are created like this:

    scala> val seq = Seq(1,2,3,4,1)
seq: Seq[Int] = List(1, 2, 3, 4, 1)

scala> val set = Set(1,2,3,4,1)
set: scala.collection.immutable.Set[Int] = Set(1, 2, 3, 4)

scala> val map = Map(1 -> "one", 2 -> "two", 3 -> "three", 2 -> "too")
map: scala.collection.immutable.Map[Int,String] = Map(1 -> one, 2 -> too, 3 -> three)

    It is also typical to prefer the scala.collection.immutable collections over those in scala.collection.mutable; the types aliased in the scala.Predef object are the immutable versions.

    Also note that the collections library was carefully designed to include several implementations of each of the three basic collection types. These implementations have specific performance characteristics which are described in the guide.

    The concrete parallel collections also have specific performance characteristics which are described in the parallel collections guide

    Converting to and from Java Collections

    The scala.collection.JavaConverters object provides a collection of decorators that allow converting between Scala and Java collections using asScala and asJava methods.

    Definition Classes
    scala
  • trait TraversableLike [+A, +Repr] extends HasNewBuilder[A, Repr] with FilterMonadic[A, Repr] with TraversableOnce[A] with GenTraversableLike[A, Repr] with Parallelizable[A, ParIterable[A]]

    A template trait for traversable collections of type Traversable[A].

    A template trait for traversable collections of type Traversable[A].

    This is a base trait of all kinds of Scala collections. It implements the behavior common to all collections, in terms of a method foreach with signature:

    def foreach[U](f: Elem => U): Unit

    Collection classes mixing in this trait provide a concrete foreach method which traverses all the elements contained in the collection, applying a given function to each. They also need to provide a method newBuilder which creates a builder for collections of the same kind.

    A traversable class might or might not have two properties: strictness and orderedness. Neither is represented as a type.

    The instances of a strict collection class have all their elements computed before they can be used as values. By contrast, instances of a non-strict collection class may defer computation of some of their elements until after the instance is available as a value. A typical example of a non-strict collection class is a scala.collection.immutable.Stream. A more general class of examples are TraversableViews.

    If a collection is an instance of an ordered collection class, traversing its elements with foreach will always visit elements in the same order, even for different runs of the program. If the class is not ordered, foreach can visit elements in different orders for different runs (but it will keep the same order in the same run).'

    A typical example of a collection class which is not ordered is a HashMap of objects. The traversal order for hash maps will depend on the hash codes of its elements, and these hash codes might differ from one run to the next. By contrast, a LinkedHashMap is ordered because its foreach method visits elements in the order they were inserted into the HashMap.

    Definition Classes
    collection
  • WithFilter

class WithFilter extends FilterMonadic[A, Repr]

A class supporting filtered operations. Instances of this class are returned by method withFilter.

Source
TraversableLike.scala
Linear Supertypes
FilterMonadic[A, Repr], AnyRef, Any
Ordering
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  2. By Inheritance
Inherited
  1. WithFilter
  2. FilterMonadic
  3. AnyRef
  4. Any
Implicitly
  1. by CollectionsHaveToParArray
  2. by any2stringadd
  3. by StringFormat
  4. by Ensuring
  5. by ArrowAssoc
  1. Hide All
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Visibility
  1. Public
  2. All

Instance Constructors

  1. new WithFilter(p: (A) ⇒ 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 to any2stringadd[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 to ArrowAssoc[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

    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 a ClassCastException at runtime, while the expression List(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 type T0.

  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[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
    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 to Ensuring[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 to Ensuring[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 to Ensuring[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 to Ensuring[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: Any): 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[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
    Note

    not specified by SLS as a member of AnyRef

  15. def flatMap[B](f: (A) ⇒ TraversableOnce[B]): Traversable[B]

    [use case] Builds a new collection by applying a function to all elements of the outer traversable collection containing this WithFilter instance that satisfy predicate p and concatenating the results.

    [use case]

    Builds a new collection by applying a function to all elements of the outer traversable collection containing this WithFilter instance that satisfy predicate p and concatenating the results.

    The type of the resulting collection will be guided by the static type of the outer traversable collection.

    B

    the element type of the returned collection.

    f

    the function to apply to each element.

    returns

    a new traversable collection resulting from applying the given collection-valued function f to each element of the outer traversable collection that satisfies predicate p and concatenating the results.

    Definition Classes
    WithFilter → FilterMonadic
    Full Signature

    def flatMap[B, That](f: (A) ⇒ GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That

  16. def foreach(f: (A) ⇒ Unit): Unit

    [use case] Applies a function f to all elements of the outer traversable collection containing this WithFilter instance that satisfy predicate p.

    [use case]

    Applies a function f to all elements of the outer traversable collection containing this WithFilter instance that satisfy predicate p.

    f

    the function that is applied for its side-effect to every element. The result of function f is discarded.

    Definition Classes
    WithFilter → FilterMonadic
    Full Signature

    def foreach[U](f: (A) ⇒ U): Unit

  17. 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 to StringFormat[WithFilter] performed by method StringFormat in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  18. final def getClass(): Class[_]

    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
  19. 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
  20. 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 return false, while the expression List(1).isInstanceOf[List[String]] will return true. 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 type T0; false otherwise.

    Definition Classes
    Any
  21. def map[B](f: (A) ⇒ B): Traversable[B]

    [use case] Builds a new collection by applying a function to all elements of the outer traversable collection containing this WithFilter instance that satisfy predicate p.

    [use case]

    Builds a new collection by applying a function to all elements of the outer traversable collection containing this WithFilter instance that satisfy predicate p.

    B

    the element type of the returned collection.

    f

    the function to apply to each element.

    returns

    a new traversable collection resulting from applying the given function f to each element of the outer traversable collection that satisfies predicate p and collecting the results.

    Definition Classes
    WithFilter → FilterMonadic
    Full Signature

    def map[B, That](f: (A) ⇒ B)(implicit bf: CanBuildFrom[Repr, B, That]): That

  22. 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
  23. 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
    Note

    not specified by SLS as a member of AnyRef

  24. 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
    Note

    not specified by SLS as a member of AnyRef

  25. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  26. def toParArray: ParArray[T]
    Implicit
    This member is added by an implicit conversion from WithFilter to CollectionsHaveToParArray[WithFilter, T] performed by method CollectionsHaveToParArray in scala.collection.parallel. This conversion will take place only if an implicit value of type (WithFilter) ⇒ GenTraversableOnce[T] is in scope.
    Definition Classes
    CollectionsHaveToParArray
  27. 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
  28. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  29. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  30. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  31. def withFilter(q: (A) ⇒ Boolean): WithFilter

    Further refines the filter for this traversable collection.

    Further refines the filter for this traversable collection.

    q

    the predicate used to test elements.

    returns

    an object of class WithFilter, which supports map, flatMap, foreach, and withFilter operations. All these operations apply to those elements of this traversable collection which satisfy the predicate q in addition to the predicate p.

    Definition Classes
    WithFilter → FilterMonadic
  32. def →[B](y: B): (WithFilter, B)
    Implicit
    This member is added by an implicit conversion from WithFilter to ArrowAssoc[WithFilter] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc

Inherited from FilterMonadic[A, Repr]

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion CollectionsHaveToParArray from WithFilter to CollectionsHaveToParArray[WithFilter, T]

Inherited by implicit conversion any2stringadd from WithFilter to any2stringadd[WithFilter]

Inherited by implicit conversion StringFormat from WithFilter to StringFormat[WithFilter]

Inherited by implicit conversion Ensuring from WithFilter to Ensuring[WithFilter]

Inherited by implicit conversion ArrowAssoc from WithFilter to ArrowAssoc[WithFilter]

Ungrouped