https://github.com/IamPawan777/Java-8-with-Stream-API

• Functional interface
• Lambda expression
• Default and Static method in interfaces.
• Stream API
• Method References : Shorthand format of lambda expression (s→s.length | String::length)
• Optional class
• Date Time API
• forEach() method

A. Functional Interface:

(Functional Interface / Lambda Expression)

Has exactly single abstract method. But more than one default and static method.

 **1- abstract method  :** not 0-abstract method & N-abstract method

N-default method

N-static method

@FunctionalInterface
public interface Calculate {
	void cal();
}

public class Main {
	public static void main(String[] args) {
		
		//1. with {}....-> when more lines
		**Calculate val = () -> {**
			System.out.println("Pawan Bisht");
			System.out.println("Harry Doi");
			System.out.println("Sam honny");
		**};**
		val.cal();

		
		// 2.without {}......when one line only
		**Calculate val = () -> System.out.println("Heelo Ho");**
		val.cal();
		}
	}

@FunctionalInterface
public interface Calculate {
	int cal(int a, int b);
}

public class Main {
	public static void main(String[] args) {
		// 3. parameterized....
		**Calculate add = (a, b) -> a+b;**
		
		System.out.println("Sum is: "+add.cal(12, 12));			
	}
}

Pre-define Interface:

1. Function → i/p: any, o/p: any
2. Predicate → i/p: any, o/p: boolean
3. Consumer → i/p: any, o.p: ❌