CODEWITHSUNDEEP
javamultithreading
St.Antario
St.Antario

Reputation: 27455

Why doesn't run method call?

I've write the following example:

public class MyThread extends Thread{
    MyThread(Runnable r){
        super(r);
    }
    public void run(){
        System.out.println("run");
    }
}
public static void main(String[] args) 
{
    Thread t = new MyThread(new Runnable() {
        @Override
        public void run() {
            System.out.println("rrrrrrrrrruuuuuuuuuuuun");
        }
    });
    t.start(); //run
}

Why does run methdo defined in MyThread was called instead?

Upvotes: 0

Views: 73

Answers (2)

willeM_ Van Onsem
willeM_ Van Onsem

Reputation: 477854

Because you the MyThread.run is not override, but the Runnable.run is. Now if you look at your implementation of MyThread.run, the stored Runnable plays no part in it. In other words, it doesn't matter what kind of runnable you give with the constructor. You should use:

public static void main(String[] args) 
{
    Thread t = new MyThread() {
        @Override
        public void run() {
            System.out.println("rrrrrrrrrruuuuuuuuuuuun");
        }
    });
    t.start(); //run
}

As @BorisTheSpider notes, overriding a Thread is in general not good practice: a Thread has the responsibility to start a Thread and give control to a runnable. A better implementation would be:

public static void main(String[] args) 
{
    Thread t = new Thread(new MyThread() {
        @Override
        public void run() {
            System.out.println("rrrrrrrrrruuuuuuuuuuuun");
        }
    }));
    t.start(); //run
}

Upvotes: 3

JB Nizet
JB Nizet

Reputation: 692231

Because the default behavior of a thread constructed with a Runnable is to delegate to the runnable passed as argument to the constructor. But you overrode run() in the thread itself, so instead of delegating to the runnable, it executes the code inside the overridden run() method.

For the record, here's the default implementation of Thread.run(), that you overrode:

private Runnable target;

public void run() {
    if (target != null) {
        target.run();
    }
}

Upvotes: 3

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