Java Function Interface

“ The Function interface generically takes a parameter of type T, executes the given job, and then returns a value of type R. “

• apply() (Abstract Method for Functional Interface) -> Applies this function to the given argument.
• compose() (Default Method)-> Returns a composed function that first applies the before function to its input, and then applies this function to the result.
• andThen() (Default Method) ->Returns a composed function that first applies this function to its input, and then applies the after function to the result.
• identity() (Default Method) -> Returns a function that always returns its input argument.

Simple syntax :

Function<T,R> func = doSomething(return R Type);

func.apply(T type param);

Lets write some examples..

/*
 * A Function interface takes the Integer parameter and returns a 
 * Double type value that returns the Square of the value;
 */
Function<Integer,Double> square = s -> Math.pow(s,2);
System.out.println(square.apply(5));
//Output : 25

We can use Unary Operator when the entered parameter and the return type are the same.

Like this ..

UnaryOperator<String> unaryOperator = s -> s.toUpperCase();
System.out.print(unaryOperator.apply("hey"));
//Output : HEY

Happy coding ..