Java Program to demonstrate the anonymous interface. | Java Program | ProwessApps

Java Program to demonstrate the anonymous interface.

Objective

Write a Java program to demonstrate an Anonymous Interface Implementation.

Algorithm / Approach

In main, declare a Runnable r = new Runnable() { ... };.
Inside the block, provide the concrete implementation for the abstract run() method.
Write the countdown logic inside the run method.
Pass the anonymous Runnable directly into a new Thread: new Thread(r).start();.

Test.java

class Test {
 public static void main(String[] a)
 {
  Runnable r= new Runnable(){ 
   public void run() {
    for(int i = 20; i>=0; i--)  { 
     System.out.printf("%02d\r",i);
     try {
      Thread.sleep(1000);
     }
     catch(Exception e) { }
    }
   }
  };
  new Thread(r).start();
 }
}

Explanation of the Program

You cannot instantiate an interface (you can't say new Runnable()).
However, the syntax new Runnable() { ... } is NOT instantiating an interface. It is telling Java to silently create a brand new, unnamed class that *implements* Runnable, and immediately return an instance of that new class.
This was the standard way to handle callbacks and events in Java before Lambda Expressions were introduced in Java 8.

Complexity

Time Complexity O(n)

Space Complexity O(1)