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)
     2.1 Runnable r = new MyRunnable()
     2.2 Runnable r = Lambda Expression
     2.3 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