Java Functional Interface Example

It belongs to java.util.function; package functional interface is defined as an interface with exactly one abstract method, some functional interfaces are :-

Function<T,R> - takes an object of type T and returns R.

Supplier<T> - just returns an object of type T.

Predicate<T> - returns a boolean value based on input of type T.

Consumer<T> - performs an action with given object of type T.

BiFunction - like Function but with two parameters.

BiConsumer - like Consumer but with two parameters. 

it also have some  interfaces for primitive data type :-

IntConsumer

IntFunction<R>

IntPredicate

IntSupplier 

public class FunctionalInterfaces {

public static void main(String[] args) {

List<Integer> list = Arrays.asList(1,2,5,8,3,6,9);

System.out.println("USE OF CUNSUMER INTERFACE TO TRAVERSE LIST");

list.forEach(new Consumer<Integer>() {

@Override

public void accept(Integer t) {

System.out.println(t);

}

});

System.out.println("\nEVEN NUMBERS FROM LIST");

Predicate<Integer> predicate = n-> n%2 == 0;

list.forEach(new Consumer<Integer>() {

@Override

public void accept(Integer t) {

if(predicate.test(t)){

System.out.println(t);

}

}

});

System.out.println("\nODD NUMBERS FROM LIST");

Predicate<Integer> oddPre = n-> n%2 != 0;

list.forEach(new Consumer<Integer>() {

@Override

public void accept(Integer t) {

if(oddPre.test(t)){

System.out.println(t);

}

}

});

System.out.println("\nNUMBERS GREATER THAN 3 IN LIST");

Predicate<Integer> pre1 = n -> n>3;

list.forEach(new Consumer<Integer>() {

@Override

public void accept(Integer t) {

if(pre1.test(t)){

System.out.println(t);

}

}

});

}

}