Java 8 Features Part -1

Java 8 introduced benefits of Functional Programming in java.

Lambda Expression :  Lambda is an anonymous function in java , a function without name ,return type and access modifier.

In java , normally we write method as below :

Example :Without Lambda

 public void run(){
	System.out.println("Welcome to www.crtr4u.com");
 }

using lambda expression same method can be written as:

    ()->System.out.println("Welcome to www.crtr4u.com");

if we have multiple statements then we can use brackets, Lambda Expression also known as anonymous function or closures.
Example : without using lambda :

 public void add(int num1,int num2){
	System.out.println(num1+num2);
 }

above example can be written using lambda expression as :

 (int num1,int num2)->System.out.println(num1+num2);

Why To Use Lambda Expression :

 1.Easy to implement and Less Code as shown in above example.

 2.We can pass lambda expression as paramater to other method.

To implement Lambda Expression in java , we have to use Functional Interface.

Functional Interface is an interface with only one abstract method,we can create our own functional interface by using annotation @FunctionalInterface.

Note - we can add many defaults method in functional interface , but only one abstract method.

Addition Example Using Lambda Expression :

@FunctionalInterface
interface DemoInterface{
	public void add(int a,int b);
}

public class Java8Demo {
	public static void main(String[] args) {
		DemoInterface d=(a,b)->System.out.println("Addition is "+(a+b));
		d.add(1, 2);
		d.add(4, 7);
	}

}

Output : 

Addition is 3 

Addition is 11

Program to check Even or Odd number using Functional Interface , Lambda Expression in Java : 

Example :

 public class Java8Demo {
	public static void main(String[] args) {
		EvenOddDemo d = (num) -> {
			if (num % 2 == 0)
				System.out.println("Even number : " + (num));
			else
				System.out.println("Odd number : " + (num));
		};
		d.isEvenOrOdd(5);
		d.isEvenOrOdd(12);
	}
 }

 @FunctionalInterface
 interface EvenOddDemo {
	public void isEvenOrOdd(int a);
 }

Output :
Odd number : 5
Even number : 12