Question

It’s quiet right that we should never override the start method of a thread but I was just practicing java when I was confused with two different behaviors…..
I’m trying to override start method of Thread class.Below is the code:

package myPackage;

public class MainThreadUsingThread extends Thread{  
    @Override  
    public void run() {  
        System.out.println("-run   in t1");  
        System.out.println("");  
    }  
    @Override  
    public void start() {

        System.out.println("in start in t1");
        super.start();
    }

    /*public static void main(String[] args) {
        System.out.println("hii");
        Thread t3=new Thread(new MainThreadUsingThread());
        t3.start();
    }*/
}

class A11 {  
    public static void main(String[] args) {  
        System.out.println("hii");  
        Thread t1=new Thread(new MainThreadUsingThread());  
        t1.start();
        Thread t2=new Thread() {
            @Override
            public void run() {  
                System.out.println("run in t2");  
            }  
            @Override
            public void start() {

                System.out.println("in start in t2");
                super.start();
            }
        };
        t2.start();
    }
}

In case of Thread “t2”, I’m getting the overridden start method but not in case of Thread “t1”.
Plz help me come out of this confusion.

Also is there any way to do the same (override, as far as it is not a good practice) in case of runnable interface.

Answer 1

Thread t1=new Thread(new MainThreadUsingThread());

Your new MainThreadUsingThread() is being used as Runnable (because Thread implements Runnable). The thread executes Runnable.run(), that’s why you don’t get the overriden start.

When Thread.start is called, it starts a new thread and call Thread.run in that new thread.

You should do this:

Thread t1=new MainThreadUsingThread();

In Thread, its run method starts the Runnable that is used to construct that Thread, or does nothing if no Runnable is used to construct it. If you extends Thread and override Thread.run, this effectively changed what the thread does.

If you use new Thread(new MainThreadUsingThread()), this effectively call the constructor Thread(Runnable target) and constructs a new Thread. Just like doing this:

Thread t1=new Thread((Runnable)(new MainThreadUsingThread()))