Thread suspending..

Question

Whats the best way of implementing a Thread so that you can start/stop the thread, and between each cycle cause the thread to sleep for a period of time ??
I have the following code, but need a way of stopping the Thread hogging all the CPU time when it is not running:
public class MyThread extends Thread()
  private int sleepPeriod = 1000; // 1000ms == 1sec
  private boolean alive = false;
  private boolean running = false;
  private void setRunning(boolean val)
    running = val;
  private boolean isRunning()
    return (running && alive);
  private void setAlive(boolean val)
    alive = val;
  private boolean isAlive()
    return (alive && super.isAlive());
  private void startThread()
    setRunning(true);
    setAlive(true);
    start();
  private void startThreadSuspended()
    setRunning(false);
    setAlive(true);
    start();
  private void run()
    while (alive) {
      while (alive && running) {
        // do work
        // Sleep
        try {
          Thread.sleep(sleepPeriod);
        } catch (Exception e) {}
      // What to put in here to force thread to sleep/wait until told to carry on
      // wait() ??
}Ive tried with a wait() where indicated above, but if i place notify() or notifyAll() in the setRunning() method, then an exception is thrown, stating that current thread is not owner of lock !??
There is some guidance at http://java.sun.com/j2se/1.4.2/docs/guide/misc/threadPrimitiveDeprecation.html, but this seems to throw the same exception !

Answer 1

The best way I think of suspending the thread is to have a shared variable (probably, static in nature). The value of this variable decides execution and suspention. For example, a boolean variable ..
public static boolean abc = false ;
// Run a thread and check the value of abc. If it is false then change the value of abc = true and do your work.
if ( abc == false )  {
  // Do you work
} else {
// Keep on sleep or wait and keep on checking the value after fix interval of wait.
}Hope this help.
Shozi
Btw: Your problem is typically related to critical section problem. I suggest you look at this topic in any operting system concepts book.