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added in API level 24

Function

public interface Function

java.util.function.Function<T, R>


Represents a function that accepts one argument and produces a result.

This is a functional interface whose functional method is apply(Object).

Summary

Public methods

default <V> Function<T, V> andThen(Function<? super R, ? extends V> after)

Returns a composed function that first applies this function to its input, and then applies the after function to the result.

abstract R apply(T t)

Applies this function to the given argument.

default <V> Function<V, R> compose(Function<? super V, ? extends T> before)

Returns a composed function that first applies the before function to its input, and then applies this function to the result.

static <T> Function<T, T> identity()

Returns a function that always returns its input argument.

Public methods

andThen

added in API level 24
public Function<T, V> andThen (Function<? super R, ? extends V> after)

Returns a composed function that first applies 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.

Parameters
after Function: the function to apply after this function is applied

Returns
Function<T, V> a composed function that first applies this function and then applies the after function

Throws
NullPointerException if after is null

See also:

apply

added in API level 24
public abstract R apply (T t)

Applies this function to the given argument.

Parameters
t T: the function argument

Returns
R the function result

compose

added in API level 24
public Function<V, R> compose (Function<? super V, ? extends T> before)

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

Parameters
before Function: the function to apply before this function is applied

Returns
Function<V, R> a composed function that first applies the before function and then applies this function

Throws
NullPointerException if before is null

See also:

identity

added in API level 24
public static Function<T, T> identity ()

Returns a function that always returns its input argument.

Returns
Function<T, T> a function that always returns its input argument