Java 8 – Method Reference | Code Factory

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Method Reference by Double Colon (::) Operator :

Method Calling by Lambda Reference :

package com.codeFactory.methodAndConstructorReference;

interface Interf {
	public void m1();
}

public class Test {
	public static void main(String... args) {
		Interf i = () -> System.out.println("Lambda Expression");
		i.m1();
	}
}

Output :

Lambda Expression

Method Calling by :: Operator :

package com.codeFactory.methodAndConstructorReference;

interface Interf {
	public void m1();
}

public class Test {
	public static void main(String... args) {
		Interf i = Test::m2;
		i.m1();
	}
	
	public static void m2() {
		System.out.println("Method Reference");
	}
}

Output :

Method Reference

• Advantage of Method Reference is code reusability.
• Referer and Refering method both should have same argument type, return type can be different, modifier can be different and that method can be static or non-static.
• Method reference is alternative syntax to Lambda Expression.
• Function Interface can refer Lambda Expression, Functional Interface can refer method reference.

Syntax for Method Reference :

• Static method :
  • classname :: method name
  • e.g. Test::m2
• Instance method :
  • object ref :: method name
  • e.g. Test t = new Test(); ——> t::m2;

How many ways we can define a thread :

1. By extend thread class
2. By implementing runnable (3 ways)
   1. Runnable r = new MyRunnable()
   2. Runnable r = Lambda Expression
   3. Runnable r = Method Reference

Thred using Lambda Expression :

package com.codeFactory.methodAndConstructorReference;

public class Test {
	public static void main(String... args) {
		Runnable r = () -> {
			for(int i=0; i<5; i++) {
				System.out.println("Child Thread");
			}
		};
		
		Thread t = new Thread(r);
		t.start();
		for(int i=0; i<5; i++) {
			System.out.println("Main Thread");
		}
	}
}

Output :

Main Thread
Child Thread
Child Thread
Child Thread
Child Thread
Child Thread
Main Thread
Main Thread
Main Thread
Main Thread

Thread using Method Reference :

package com.codeFactory.methodAndConstructorReference;

public class Test {
	public void m1() {
		for(int i=0; i<5; i++) {
			System.out.println("Child Thread");
		}
	}
	
	public static void main(String... args) {
		Test t = new Test();
		Runnable r = t :: m1;
		Thread t1 = new Thread(r);
		//Thread t1 = new Thread(new Test()::m1);
		t1.start();
		for(int i=0; i<5; i++) {
			System.out.println("Main Thread");
		}
	}
}

Output :

Main Thread
Main Thread
Main Thread
Main Thread
Main Thread
Child Thread
Child Thread
Child Thread
Child Thread
Child Thread

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