Function

  • Function is a functional interface representing a function accepting one argument and producing a result.

  • It includes methods like apply, which executes the function on an argument, and compose/andThen for chaining functions.

  • identity is a static method that returns a function returning its input unchanged.
public interface Function
Known Indirect Subclasses

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

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

Public Method Summary

<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.
<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

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 the function to apply after this function is applied
Returns
  • a composed function that first applies this function and then applies the after function
Throws
NullPointerException if after is null
See Also

public abstract R apply (T t)

Applies this function to the given argument.

Parameters
t the function argument
Returns
  • the function result

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 the function to apply before this function is applied
Returns
  • a composed function that first applies the before function and then applies this function
Throws
NullPointerException if before is null
See Also

public static Function<T, T> identity ()

Returns a function that always returns its input argument.

Returns
  • a function that always returns its input argument