如何让 ThreadPoolExecutor 使用双端队列？

Question

我需要一个线程池，它可以接收要插入到队列后面（像往常一样）或队列前面（用于优先任务）的任务。然后应该正常执行任务，从队列的头部轮询。

我意识到这意味着使用BlockingDeque 创建我自己的ThreadPoolExecutor，但这还不够……我如何真正告诉线程池调用队列的offerFirst 方法而不是offer？

Answer 1

您需要将PriorityBlockingQueue 传递给ThreadPoolExecutor，可能使用此构造函数。下面添加了如何使用比较器初始化 PriorityBlockingQueue 的示例

public ThreadPoolExecutor(int corePoolSize,
                          int maximumPoolSize,
                          long keepAliveTime,
                          TimeUnit unit,
                          BlockingQueue<Runnable> workQueue) {
    this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
         Executors.defaultThreadFactory(), defaultHandler);
}

编辑 - 将比较器添加到优先级队列的示例

import java.util.Comparator;
import java.util.concurrent.PriorityBlockingQueue;
import java.util.concurrent.BlockingQueue;

public class PriorityBlockQueueTest {

    private static BlockingQueue<PriorityTask> taskQueue = new PriorityBlockingQueue<>(10,
            new Comparator<PriorityTask>() {
        @Override
        public int compare(PriorityTask o1, PriorityTask o2) {
            return o2.getData() - o1.getData();
        }
    });

    public static void main(String arg[]) {
        taskQueue.add(new PriorityTask(2, 10));
        taskQueue.add(new PriorityTask(1, 11));

        System.out.println(taskQueue);
    }

    private static class PriorityTask implements  Runnable {
        private int priority;
        private int data;
        public PriorityTask(int priority, int data) {
            this.priority = priority;
            this.data = data;
        }

        public int getData() {
            return data;
        }

        public void run() {
            System.out.println("Running something");
        }

        public String toString() {
            return "priority: " + priority + " data: " + data;
        }
    }
}