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
  • sealed abstract class Option[+A] extends Product with Serializable

    Represents optional values.

    Represents optional values. Instances of Option are either an instance of scala.Some or the object None.

    The most idiomatic way to use an scala.Option instance is to treat it as a collection or monad and use map,flatMap, filter, or foreach:

    val name: Option[String] = request getParameter "name"
val upper = name map { _.trim } filter { _.length != 0 } map { _.toUpperCase }
println(upper getOrElse "")

    Note that this is equivalent to 

    val upper = for {
  name <- request getParameter "name"
  trimmed <- Some(name.trim)
  upper <- Some(trimmed.toUpperCase) if trimmed.length != 0
} yield upper
println(upper getOrElse "")

    Because of how for comprehension works, if None is returned from request.getParameter, the entire expression results in None

    This allows for sophisticated chaining of scala.Option values without having to check for the existence of a value.

    These are useful methods that exist for both scala.Some and None.

    • isDefined — True if not empty
    • isEmpty — True if empty
    • nonEmpty — True if not empty
    • orElse — Evaluate and return alternate optional value if empty
    • getOrElse — Evaluate and return alternate value if empty
    • get — Return value, throw exception if empty
    • fold — Apply function on optional value, return default if empty
    • map — Apply a function on the optional value
    • flatMap — Same as map but function must return an optional value
    • foreach — Apply a procedure on option value
    • collect — Apply partial pattern match on optional value
    • filter — An optional value satisfies predicate
    • filterNot — An optional value doesn't satisfy predicate
    • exists — Apply predicate on optional value, or false if empty
    • forall — Apply predicate on optional value, or true if empty
    • contains — Checks if value equals optional value, or false if empty
    • toList — Unary list of optional value, otherwise the empty list

    A less-idiomatic way to use scala.Option values is via pattern matching: 

    val nameMaybe = request getParameter "name"
nameMaybe match {
  case Some(name) =>
    println(name.trim.toUppercase)
  case None =>
    println("No name value")
}

    Interacting with code that can occasionally return null can be safely wrapped in scala.Option to become None and scala.Some otherwise. 

    val abc = new java.util.HashMap[Int, String]
abc.put(1, "A")
bMaybe = Option(abc.get(2))
bMaybe match {
  case Some(b) =>
    println(s"Found $b")
  case None =>
    println("Not found")
}
    Definition Classes
    scala
    Annotations
    @SerialVersionUID()
    Since

    1.1

    Note

    Many of the methods in here are duplicative with those in the Traversable hierarchy, but they are duplicated for a reason: the implicit conversion tends to leave one with an Iterable in situations where one could have retained an Option.

  • WithFilter
c

scala.Option

WithFilter

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
Option.scala
Linear Supertypes
AnyRef, Any
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. WithFilter
  2. AnyRef
  3. Any
Implicitly
  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. 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[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @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 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[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) ⇒ Option[B]): Option[B]
  16. 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
    Annotations
    @native()
  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
    Annotations
    @native()
  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): Option[B]
  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
    Annotations
    @native()
    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
    Annotations
    @native()
    Note

    not specified by SLS as a member of AnyRef

  25. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  26. 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
  27. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  28. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  29. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  30. def withFilter(q: (A) ⇒ Boolean): WithFilter
  31. 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 AnyRef

Inherited from Any

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