Function

public interface Function

java.util.function.Function<T, R>

Known indirect subclasses

UnaryOperator<T>

UnaryOperator<T> Represents an operation on a single operand that produces a result of the same type as its operand.

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

This is a functional interface whose functional method is apply(java.lang.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:

compose(Function)

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:

andThen(Function)

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