Interrupting a Thread

[Sreeram Desigan]

consider the following program
class A extends Thread {
public void run() {
try {
synchronized (this) {
wait();
}
} catch (InterruptedException ie) {
System.out.println("isInterrupted() inside catch is " + isInterrupted());
}
}
public static void main(String[] args) {
A a1 = new A();
a1.start();
a1.interrupt();
System.out.println("a1.isInterrupted() inside main is " + a1.isInterrupted());
}
}

--------
one of the output for this program is :
a1.isInterrupted() inside main is true
a1.isInterrupted() inside catch is false

why is this an output. As for the specification of thread method isInterrupted() method never resets the Interrupt flag of a thread.

[Vinayagar Karpagam]

This is given in java doc.

If this thread is blocked in an invocation of the {@link
* Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link
* Object#wait(long, int) wait(long, int)} methods of the {@link Object}
* class, or of the {@link #join()}, {@link #join(long)}, {@link
* #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)},
* methods of this class, then its interrupt status will be cleared and it
* will receive an {@link InterruptedException}.

I think this is the reason why the isInterrupted() is false.

[Sreeram Desigan]

But y is the first isInterrupted() in main immediately after interrupt() returns true.
I guess interrupt() method will set the interrupt status to true and moves thread a1 from waiting status to ready status. The main thread after executing this interrupt on thread a1 will call the isinterrupt() method which will check the status and return true. Now when the thread a1 moves from ready status to execution status it will throw InterruptedException and reset the Interrupt status. Thus the isInterrupted() method in the catch block will return false.
This what i guess has happened but i want a clear proof of it. Thats y i posted this question to know different views on it. But received no replies at all.

[Vinayagar Karpagam]

I tried modifying the main() like this :

public static void main(String[] args) {
A a1 = new A();
a1.start();
a1.interrupt();
try{
Thread.sleep(500);
}catch(InterruptedException ex){}
System.out.println("a1.isInterrupted() inside main is " + a1.isInterrupted());
}
}

when i run this program, i got o/p as

first line, catch will print false;
next line, main will print false;

so, without sleep() called, main completes before exception is thrown & prints true.

and with sleep() called, catch completes after exception is thrown & prints false.