Thread Doubt

[Divya Gehlot]

O/p of below porogram is
MyThread: start()
MyRunnable: run()
Can any one explain why o/p is not
MyThread: start()
MyThread: run()
MyRunnable: start()
MyRunnable: run()

 class MyThread extends Thread
{
public void run()
{
System.out.println("MyThread: run()");
}
public void start()
{
System.out.println("MyThread: start()");
}
}
class MyRunnable implements Runnable
{
public void run()
{
System.out.println("MyRunnable: run()");
}
public void start()
{
System.out.println("MyRunnable: start()");
}
}
public class MyTest
{
public static void main(String args[])
{
MyThread myThread = new MyThread();
MyRunnable myRunnable = new MyRunnable();
Thread thread = new Thread(myRunnable);
myThread.start();
thread.start();
}
}
   

[Praveen Seluka]

Hi divya

I will try my best to answer.

mythread.start()
The above statement is not starting the new thread.It just calls the overridden start() method in MyThread class.

Thats why you got the output : MyThread: start()

thread.start();
This statement starts the newly created thread.This will access start() method declared in Thread class which in turn calls run() method declared in MyRunnable class which results in the output MyRunnable: run()

mythread.start() calls the start() of MyThread alone
thread.start() calls the start() of Thread class which calls run() of MyRunnable.

Thanks
Praveen SP

[dolly shah]

I got the output. But I have another question. Why MyRunnable class is able to implement start() method. It is not a Runnable interface method.
can you explain?

[Henry Wong]

Originally posted by dolly shah:
I got the output. But I have another question. Why MyRunnable class is able to implement start() method. It is not a Runnable interface method.
can you explain?

For the same reason the MyRunnable class is able to implement a method named join(), alive(), hello(), goodbye(), mymethod1(), mymethod2(), etc. Just because you implement an interface, doesn't mean that you are not allowed to have methods that is not part of that interface.

Henry

[dolly shah]

Even Object class doesn't have start() method. From where MyRunnable can implement this method?

[Michael Sanchez]

A class may define new methods - there is no requirement that methods defined in a class be first declared in an interface.

However, *if* a class *does* implement an interface, then it must implement all of the methods declared in that interface (or be declared abstract itself).