Thread problem

[neha verma]

Hi,
Can somebody explain the output for the code below. I dont think if we can call the run method explicity. it is implicitly called when start() method is invoked.
Thanks in advance.

 class A implements Runnable {
  public void run() {System.out.print(Thread.currentThread().getName());}
}
class B implements Runnable {
  public void run() {
    new A().run();
    new Thread(new A(),"T2").run();
    new Thread(new A(),"T3").start();
}}
class C {
  public static void main (String[] args) {
    new Thread(new B(),"T1").start();
}}
 
What is the result of attempting to compile and run the program? 
 
a.  Prints: T1T1T1 
b.  Prints: T1T1T2 
c.  Prints: T1T2T2 
d.  Prints: T1T2T3 
e.  Prints: T1T1T3 
f.  Prints: T1T3T3 
g.  Compile-time error 
h.  Run-time error 
i.  None of the above 
Answer : T1T1T3
  

[Praveen Seluka]

Hi neha

First of all,we can explicitly call run().Its just like some other x() in a class.
But note that calling the run() in the code does not start a new Thread.

new A().run();
This calls the run() method and doesnot start a new thread.

A new thread starts running only by calling the start() method.

Thanks
Praveen SP

[Mack Stevens]

HI.........................

First of all make it clear that we can call a run() method explicitly.
But sun microsystem programmers have written a lots of code in start() method in native languauges for allocation of memory and for certain other important criteria.So they suggest using start() method for invoking a thread.If we are using run() method for invoking thread there might occur some problem with your code in the operating syatem environment.

[Gitesh Ramchandani]

Neha, it is very simple.

When you call run() directly it does not create a new thread. Calling start() only creates a new thread.

So in the code below you start a new thread with name T1. Then:
new A().run();---just calls run(), no new thread
new Thread(new A(),"T2").run();---just calls run(), no new thread
new Thread(new A(),"T3").start();-----creates a new thread with name T3

class B implements Runnable {
  public void run() {
    new A().run();
    new Thread(new A(),"T2").run();
    new Thread(new A(),"T3").start();
}}
class C {
  public static void main (String[] args) {
    new Thread(new B(),"T1").start();

Hope i'm able to provide some meaningfool explanation.

regards,
Gitesh