Why a thread can not be restarted?????

Question

Hi,
I have a thread and I started it by claling thread.start() and some where in my code i want to say thread.start(), which jvm won't allow me to do so... could u please reason me elaborately?????????
Thanks
Sato.

Answer 1

Essentially once a Thread has been started it cannot be started again regardless of its current running state.
Calling start on a started Thread makes no sense. Neither does calling start on a Thread that has finished make sense although for less obvious reasons.
You can query a Thread to see if it is still active (has been started and not yet completed) via the isAlive() method.
You can then query the Thread you want to start with code like this
if(!myThread.isAlive()) {
    myThread.start();
}This code works fine when the Thread is still running however what happens when the Thread has run to completion?
Well it is often best to offer more complete state information about your Thread class...
class MyThread extends Thread {
    boolean hasRun;
    public MyThread() {
        this.hasRun = false;
    public void start() {
        super.start();
        this.hasRun = true;
    public boolean hasRun() {
        return this.hasRun;
    public void run() {
if(!myThread.isAlive() && !myThread.hasRun()) {
    myThread.start();
}In this way you can not only see if instances of your Thread class are currently active but also if they have completed.
As to the rest of you posters, why pick on him like that? If you don't know the answers then don't post anything.