I am getting rid of waiting:
public void run() {
while(!running) {} //active waiting
//some action after running is true
}
My code:
class MyThread implements Runnable {
protected boolean running = false;
public Object lock = new Object();
@Override
public void run() {
while(!running) {
synchronized(lock) {
try {
lock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}//end lock
}
//main job which will be done when the flag running is true
}//end run
public void managerStateChanged (Manager m) {
if(m.getState() == 1) {
this.running = true;
synchronized(lock) {
lock.notify();
}
}
}
}
class Manager {
protected MyThread listener = null;
protected int state = 0;
public int getState() { return state; }
public void registerListener(MyThread l) {
listener = l;
}
public void managerStateChanged() {
if(listener != null) {
listener.managerStateChanged(this);
}
}
}
Edit:
1) For all - be careful when using this, both wait() and notify() must be wrapped in synchronized block otherwise it will raise IlegalMonitorException, when you have it in your code and still getting this exception search again, there is probably called another notify somewhere else without this synchronized block. Thank to the comments.
2) I modified the question since my code was ok but sh** happens and I forgot delete something somewhere. This is working fine. The question is my implementation correct?
There are some points that I am not fully sure about:
- I get rid of active waiting by wait and notify on some object
- When the program evaluation comes to the while loop the thread is asleep on the object, thread does do anything and active waiting is replaced by passive waiting so it's much better for CPU.
- When on Manager happens change of the state and its corresponding method managerStateChanged() is called, it's called same method on sleepting thread MyThread which will check if its the state we are waiting for, if not the thread is still sleeping if yes the running flag is changed and the thread is woken up, the while loop condition is no more loop and we jump out of passive waiting and the thread continues with its useful code after the while loop
- There is one more thing that should be considered and its spurious wakeup, that the thread can be woken up before notify, I hope that this is should not be problem here because if its woken up before notify the passive while loop condition is still not met so it falls asleep again and the spurious wake up should not be problem.
Are my guesses about this right? Is the code clear? Didn't I miss something what should be treated better? I hope not. Thanks for replies.
