java - 我如何设置 DelayQueue 的延迟

Question

我刚开始用 java 编码，我正在努力设置 DelayQueue，

我想这样，

DelayQueue queue = new DelayQueue();

If (counter > 0){
queue.offer(Integer, *A custom delay*)
} Else {
queue.offer(Integer, *A different custom delay*)
}

我只是想学习所有基础知识，我已经通读了 API，但似乎无法掌握它。

提前致谢

Answer 1

Delayed 的这种实现很好，因为:

• compareTo() 的实现不进行任何类转换，消除了抛出 ClassCastException
的可能性
• compareTo() 的实现在转换为 int 之前使用 Math.min 和 Math.max 函数为了正确防止溢出错误
• getDelay() 的实现正确地转换了单位并实际返回剩余时间

TestDelay 类实现Delayed:

import org.jetbrains.annotations.NotNull;

import java.util.concurrent.Delayed;
import java.util.concurrent.TimeUnit;

public class TestDelay implements Delayed
{
    public final Long delayMillis;
    public final Long expireTimeMillis;

    public TestDelay(Long delayMillis)
    {
        this.delayMillis = delayMillis;
        this.expireTimeMillis = System.currentTimeMillis()+delayMillis;
    }

    @Override
    public final int compareTo(@NotNull Delayed o)
    {
        long diffMillis = getDelay(TimeUnit.MILLISECONDS)-o.getDelay(TimeUnit.MILLISECONDS);
        diffMillis = Math.min(diffMillis,1);
        diffMillis = Math.max(diffMillis,-1);
        return (int) diffMillis;
    }

    @Override
    public final long getDelay(@NotNull TimeUnit unit)
    {
        long delayMillis = expireTimeMillis-System.currentTimeMillis();
        return unit.convert(delayMillis,TimeUnit.MILLISECONDS);
    }
}

JUnit 单元测试显示了使用 TestDelay 类的示例:

import org.junit.Test;

import java.util.concurrent.DelayQueue;

public class DelayQueueTest
{
    @Test
    public final void generalTest() throws InterruptedException
    {
        DelayQueue<TestDelay> q = new DelayQueue<>();
        q.put(new TestDelay(500L));
        q.put(new TestDelay(2000L));
        q.put(new TestDelay(1000L));
        q.put(new TestDelay(10L));
        q.put(new TestDelay(3000L));
        while (!q.isEmpty())
        {
            System.out.println(q.take().delayMillis);
        }
    }
}

DelayQueueTest 的输出: