SCJP / strange behaviour when using Thread-Constructor

[Guido Ranft]

I thought when I create an extended thread instance with a constructor object implementing runnable
the run-method of the constructor instance is used. Instead the overriden method is used. Why?

public class TestA extends Thread {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub

		// why does java use the overriden method
		// in the first case?
	 
		new TestA(new TestB(),"call 1").start();

		new Thread(new TestB(),"call 2").start();
	}
	
	TestA(Runnable runnable, String name)
	{
		super(runnable,name);
	}
	
	public void run()
	{
		System.out.println("TestA "+Thread.currentThread().getName());
		
	}
	
	

}
class TestB implements Runnable
{
	public void run()
	{
		System.out.println("TestB "+Thread.currentThread().getName());
	}
}

[Rob Spoor]

Welcome to the Ranch! Could you please UseCodeTags next time?

Anyway, when a Thread is started, its run() method is executed in a new thread. The default behaviour is to call the run() method of its Runnable. Since you've overridden the method you don't get that behaviour anymore. A simple fix is to call super.run() inside your run() method.

[Istvan Kovacs]

You are asking the wrong question. The question you should be asking is "Why does Thread run the supplied Runnable?". (Tip: read its source code.) Once you figure that out, you'll know the answer to your question.