Functional Interfaces in java 8

A functional interface is an interface that contains only one abstract method. 

Along with the one abstract method, they can have any number of default and static methods.

In Java 8 there are four types of Functional Interfaces.

1) Predicate
2) Consumer
3) Function
4) Supplier

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1) Predicate gives only boolean value on the basis of one argument,
   it has only one method called test().
   
   class PredicateExample {

    public static void main(String[] args) {

    Predicate<String> checkLength = t->t.length()>3;
    System.out.println(checkLength.test("Aman"));

     }

  }
   
   // Result will be : true
   
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2) Consumer only Consumes data and no output will be send.
   It has only one method called accept().
   
   class Employees{

        String name;

        public String getName() {
           return name;
        }
        public void setName(String name) {
            this.name = name;
        }
   }

  public class ConsumerExample {

    public static void main(String[] args) {

        Employees e =new Employees();
        Consumer<Employees> getNames = t->t.setName("Ajay Kumar Dargan");
        getNames.accept(e);
        System.out.println(e.getName());

     }

  }
 
  // Result will be : Ajay Kumar Dargan
 
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3) Function it has two arguments like Function(T , R)
   'T' represent as input and 'R' represent as output.
    It has only one method called apply().


public class FunctionExample {

     public static void main(String[] args) {

     Function<Integer,String> multiply = m->m*10+" << Multiply by 10";
        System.out.println(multiply.apply(20));

  }

}

//Result : 200 << Multiply by 10
--------------------------------------------------------------  
 
  4) Supplier does not take any arguments, but it only gives output.
     It has only one method called get().

    public class SupplierExample {

      public static void main(String[] args) {

      Supplier<Double> getRendumNum = ()->Math.random();
      System.out.println(getRendumNum.get());
    }

  }

Result : 0.1384031347391398
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