我有以下据称是 DelayQueue 的简单演示。
class DelayedThing implements Delayed {
private final long waitUntil;
private final String name;
public DelayedThing(String name, long wait) {
this.name = name;
this.waitUntil = System.currentTimeMillis() + wait;
System.out.println("DelayedThing(" + name + " wait=" + wait + " until-" + waitUntil);
}
@Override
public long getDelay(TimeUnit unit) {
System.out.println(name + " getDelay = " + unit.convert(waitUntil - System.currentTimeMillis(), TimeUnit.MILLISECONDS));
return unit.convert(waitUntil - System.currentTimeMillis(), TimeUnit.MILLISECONDS);
}
@Override
public int compareTo(Delayed o) {
long diff = this.getDelay(TimeUnit.MILLISECONDS) - o.getDelay(TimeUnit.MILLISECONDS);
System.out.println(name + ".compareTo(" + o + ") = " + diff);
return Long.signum(diff);
}
@Override
public String toString() {
return name;
}
}
public void test() throws InterruptedException {
BlockingQueue<Delayed> queue = new DelayQueue<>();
queue.add(new DelayedThing("one second", 1000));
queue.add(new DelayedThing("two seconds", 2000));
queue.add(new DelayedThing("half second", 500));
for (Delayed d : queue) {
System.out.println(d);
}
}
但它打印
half second
two seconds
one second
这显然是错误的。
最佳答案
这个错误是一个微妙的错误。我假设 iterator
的 DelayQueue
将为每个元素执行一系列 take
调用。 错!
请参阅 iterator() JavaDoc:
这是相当出乎意料的。
一种正确的解决方案如下:
while (queue.size() > 0) {
System.out.println(queue.take());
}
请注意,如果您尝试流式传输队列,也会发生此问题:
queue.stream().forEach((d) -> {
System.out.println(d);
});
由于流将发生在
iterator
提供的 DelayQueue
上,这也会产生意想不到的结果。关于java - 为什么我的 DelayQueue 没有以错误的顺序延迟和打印?,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/32206562/