thread doubt??

[Karu Raj]

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

the answer is( e.)Prints: T1T1T3
Please explain me why ?

Edited by Corey McGlone: Added CODE Tags
[ September 07, 2005: Message edited by: Corey McGlone ]

[marc weber]

What happens when you call a Thread's run method directly (as opposed to calling start)?

[shameena Hussain]

when the thread's run() method is called directly,it doesn't start a new thread...it ll run the existing thread... so, t1 is printed the second time also

[raghu babu]

In class C,

new Thread(new B(),"T1").start();

starts a new thread named T1, and this start invokes run method of
class B.

class B's run method is :
new A().run(); <== call class A's run method
<== and class A's run method prints the
<== name of current executing thread
<== and currently executing thread is T1

new Thread(new A(),"T2").run();
<== This statement is creating a new Thread
<== and calling run method of Thread directly
<== Note : run method called in this statement
<== none of the run methods coded here, but
<== the one coded in java.lang.Thread and
<== which calls the run method of Runnable
<== passed in the constructor and this is
<== A's run method. ( This statement calls
<== run method directly so no new thread
<== is spawned in statement. ) So, A's run
<== method still prints T1 as that is the only
<== thread still executing, so T1 is printed
<== again
new Thread(new A(),"T3").start();
<== This spawns a new thread named T3 and by now
<== it should be clear why T3 is printed

Hope this clarifies the confusion.

[raghu babu]

What happens when you call a Thread's run method directly (as opposed to calling start)?

This means you are not spawning a Thread and run method is executed
normally as any other method would.

[marc weber]

Originally posted by raghu babu:
What happens when you call a Thread's run method directly (as opposed to calling start)?

This means you are not spawning a Thread and run method is executed
normally as any other method would.

Or, more precisely, the method body would execute in the current thread.