could you pls explain this code and the output.

[Supriya Nimakuri]

What will happen when you attempt to compile and run the following code?

How will a b.run(); a valid condition. instead of b.start();

public class Bground extends Thread{
public static void main(String argv[]){
Bground b = new Bground();
b.run();
}
public void start(){
for (int i = 0; i <10; i++){
System.out.println("Value of i = " + i);
}
}
}

1) A compile time error indicating that no run method is defined for the Thread class
2) A run time error indicating that no run method is defined for the Thread class
3) Clean compile and at run time the values 0 to 9 are printed out
4) Clean compile but no output at runtime

[Peter MacMillan]

As written, that code will compile and run cleanly without any output (4).

To understand why, examine the java API for the Thread.start and Thread.run methods.

As a hint, here is a modified version that will produce output:

public class Bground extends Thread {
    public static void main(String argv[]) {
        Bground b = new Bground();
        b.start();
    }
 
    public void run() {
        for (int i = 0; i < 10; i++) {
            System.out.println("Value of i = " + i);
        }
    }
}

hint: the default run method is essentially empty (well, it will try to use a delegate Runnable, but that's not applicable in this case). The code from your question overrides the start() method and calls the Thread.run() method.

Hope that helps.
[ June 27, 2006: Message edited by: Peter MacMillan ]

[wise owen]

How will a b.run(); a valid condition. instead of b.start();

Can the run() Method Be Called Directly to Start a Thread?