Type Parameters:

T - the type of the input to the function

R - the type of the result of the function

All Known Subinterfaces:

UnaryOperator<T>

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface Function<T,R>

Since:

1.8

• Method Summary

  All Methods Static Methods Instance Methods Abstract Methods Default Methods 

  Modifier and Type	Method	Description
  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.
  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.

• Method Detail

  • apply

    R apply(T t)

    Applies this function to the given argument.

    Parameters:

    t - the function argument

    Returns:

    the function result

  • compose

    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. If evaluation of either function throws an exception, it is relayed to the caller of the composed function.

    Type Parameters:

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

    andThen(Function)

  • andThen

    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. If evaluation of either function throws an exception, it is relayed to the caller of the composed function.

    Type Parameters:

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

    compose(Function)

  • identity

    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