Runnable vs Thread

[Shreesha Kramadhary]

Why does extended thread's run() is chosen over Runnable's run()

public class AnonymousThreads {

	
	public static void main(String[] args) {
              Runnable r = new Runnable() {
			
			@Override
			public void run() {
				System.out.println("Cat");
				
			}
		};

		Thread t = new Thread(r){
			public void run() {
				System.out.println("Dog");
			}
		};
		
		
		t.start();
	}

}

Ouput
Dog

[Himai Minh]

Thread t = new Thread(r){....}
What is t refering to ? A Thread or an anonymous subclass of Thread?
Thread t is refering to A Thread, which has a run method that prints "Dog".
Just like
We have Animal class and its subclass Cat.
Animal has eat(). Cat overrides eat().
Animal a =new Cat();
a.eat();
What is the result? It calls the eat method of Animal, not Cat.

[Seetharaman Venkatasamy]

Hmm, because it is t.start(); not r.start() . clear more ?

[Seetharaman Venkatasamy]

Welcome to CodeRanch Shreesha Kramadhary

[Kevin Florish]

Himai Minh wrote:
We have Animal class and its subclass Cat.
Animal has eat(). Cat overrides eat().
Animal a =new Cat();
a.eat();
What is the result? It calls the eat method of Animal, not Cat.

Actually it calls the eat method of Cat, because with overrides the actual object type of Cat is dynamically called at runtime, not the reference type of Animal

[Matthew Brown]

By default, the run() method of a Thread will delegate that call to the run() method of the Runnable passed into it (if anything was).

But this case isn't using the default. You've overridden Thread.run() in that instance to do something else. So it's going to do something else.

[Himai Minh]

Kevin Florish wrote:
Actually it calls the eat method of Cat, because with overrides the actual object type of Cat is dynamically called at runtime, not the reference type of Animal

Thanks, Kevin.

By the way, let me do it again.
Thread t actually overrides the run method that prints "Dog", like Animal a = new Cat(); a.eat(); This eat() is the Cat's eat(), not its parent's eat.
Why r's run() is not called? If your Cat class has an attribute , such as int claw that Animal class does not have, Animal class knows nothing about that Cat's claw.

class Animal{
     protected void eat() {....}


     public static void main(String[] args){
          Animal a = new Cat(4);
         a.getClaw();  //won't compile.
    }
}

class Cat extends Animal{
      int claw;
      Cat(int claw){this.claw=claw};
      protected void eat(){...}
      protected int getClaw( ){....}
}

The same thing here:

public class AnonymousThreads {   
  
       
    public static void main(String[] args) {   
              Runnable r = new Runnable() {   
               
            @Override  
            public void run() {   
                System.out.println("Cat");   
                   
            }   
        };   
   
       // Thread t knows nothing about r. So , t.start() calls the overriding run method, but not r's run() method.
        Thread t = new Thread(r){   
            public void run() {   
                System.out.println("Dog");   
            }   
        };   
           
           
        t.start();   
    }   
  
}  

[Bhoopendra Singh]

Matthew is correct. You overriding default behaviour of Thread's Run method. So this method is doing what you are asking to do.