java - 一个线程计时比其他线程快

Question

我有一个线程每秒重复一个 Action (射击):

long lasttime;
Creature owner;
public Attacker(Creature actor)
{
    super("Attacker - "+actor.getClass().getSimpleName());
    lasttime=System.currentTimeMillis();    
    owner=actor;
    owner.lockedon=true;
}
@Override
public void run() {
    super.run();
    while(!owner.dead && owner.lockedon)
    {
        List pl=TVS.getGameScreen().projectiles;
        synchronized (pl)
        {
           //here
            long curtime=System.currentTimeMillis();
            if(curtime-lasttime>1000)
            {
                owner.attack();
                lasttime=curtime;
            }
        }
    }
}

但是当主程序线程变慢时，该线程的执行速度比主线程快，并且射击相对于主线程变得过于频繁。我该怎么办？

Answer 1

您正忙于等待，持有一个锁，这可能会消耗大量 CPU，或者锁定尝试使用同一锁的其他线程。我建议类似

while(!owner.dead && owner.lockedon) {
    List pl=TVS.getGameScreen().projectiles;
    long curtime=System.currentTimeMillis();
    long remaining = 1000 - (curtime-lasttime);
    if(remaining <= 0) {
        synchronized (pl) { // only lock when needed.
            owner.attack();
            lasttime=curtime;
        }
    } else {
        // when not doing something useful, give up the CPU to another thread.
        Thread.sleep(remaining);
    }
}