java8.util.function

Class Functions

java.lang.Object

java8.util.function.Functions

public final class Functions
extends java.lang.Object

A place for static default implementations of the new Java 8 default interface methods and static interface methods in the Function interface.

Method Summary

Modifier and Type	Method and Description
static <R,T,V> Function<T,V>	andThen(Function<? super T,? extends R> this_, Function<? super R,? extends V> after) Returns a composed function that first applies the this_ function to its input, and then applies the after function to the result.
static <R,T,V> Function<V,R>	compose(Function<? super T,? extends R> this_, Function<? super V,? extends T> before) Returns a composed function that first applies the before function to its input, and then applies the this_ function to the result.
static <T> Function<T,T>	identity() Returns a function that always returns its input argument.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

compose

public static <R,T,V> Function<V,R> compose(Function<? super T,? extends R> this_,
                                            Function<? super V,? extends T> before)

Returns a composed function that first applies the before function to its input, and then applies the this_ function to the result. If evaluation of either function throws an exception, it is relayed to the caller of the composed function.

Type Parameters:

R - the type of the result of the this_ function and of the composed function

T - the type of the input to the this_ and of the result of the before function

V - the type of input to the before function, and to the composed function

Parameters:

this_ - the function to apply after the before function is applied

before - the function to apply before the this_ function is applied

Returns:

a composed function that first applies the before function and then applies the this_ function

Throws:

java.lang.NullPointerException - if this_ is null

java.lang.NullPointerException - if before is null

See Also:

andThen(Function, Function)

andThen

public static <R,T,V> Function<T,V> andThen(Function<? super T,? extends R> this_,
                                            Function<? super R,? extends V> after)

Returns a composed function that first applies the this_ function to its input, and then applies the after function to the result. If evaluation of either function throws an exception, it is relayed to the caller of the composed function.

Type Parameters:

R - the type of the result of the this_ function and of the input to the after function.

T - the type of the input to the this_ function and to the composed function

V - the type of output of the after function, and of the composed function

Parameters:

this_ - the function to apply before the after function is applied

after - the function to apply after the this_ function is applied

Returns:

a composed function that first applies the this_ function and then applies the after function

Throws:

java.lang.NullPointerException - if this_ is null

java.lang.NullPointerException - if after is null

See Also:

compose(Function, Function)

identity

public static <T> Function<T,T> identity()

Returns a function that always returns its input argument.

Type Parameters:

T - the type of the input and output objects to the function

Returns:

a function that always returns its input argument