compose() and andThen() methods in java.util.function.Function (Java Platform SE 8 )

Source:

https://docs.oracle.com/javase/8/docs/api/java/util/function/Function.html#compose-java.util.function.Function-

• 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)