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Thread Weirdness

msulli1355 Posted: Tue Apr 27, 2004 8:37 am

Joined: 17 Apr 2004

Posts: 28

Thread Weirdness

Can anyone explain this to me: I think I`ve got the code right, thanks
to the generous example sent to me, but I can`t figure out the cause of
the following test results:

Battle class:

AllyParty ap;

ap.ally[0].advance();
ap.ally[0].retreat();

Ally class:

public synchronized void threadAdvance()
{
System.out.println("Advancing");
hasAdvanced = false;
while (getXPos() > 350)
{
moveLeft(20);
setCurrentImage(WALK);
battle.repaint();
try { Thread.sleep(200); } catch (Exception e) {}
setCurrentImage(STAND);
battle.repaint();
try { Thread.sleep(200); } catch (Exception e) {}
}
System.out.println("Done advancing");
hasAdvanced = true;
this.notifyAll();
}

public synchronized void threadRetreat()
{
while (hasAdvanced == false)
{
try
{
this.wait();
}
catch (InterruptedException e) {}
}
System.out.println("Retreating");
while (getXPos() <= 500)
{
moveRight(20);
setCurrentImage(WALK);
battle.repaint();
try { Thread.sleep(200); } catch (Exception e) {}
setCurrentImage(STAND);
battle.repaint();
try { Thread.sleep(200); } catch (Exception e) {}
}
notifyAll();
}

Test results:

Test Condition: Control group
Test Result: No visible movement of sprite. No console messages
(Was expecting "Advancing" "Retreating")

Test Condition Commented out ap.ally[0].retreat()
Test Result Perfect visual effect. All expected console
messages present.

Test Condition Comment out ap.ally[0].advance(), uncommenting
ap.ally[0].retreat()
Test Result Same result as Control group

Conclusion: Confusion

The case with retreating without advancing makes sense, as does
advancing without retreating, but why doesn`t nothing happen when both
lines are compiled? If you can find the error in my logic then please
help me!!!!

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