PriorityBlockingQueue详解

1.PriorityBlockingQueue

public class PriorityBlockingQueue<E>
extends AbstractQueue<E>
implements BlockingQueue<E>, Serializable

　　所有添加进入PriorityBlockingQueue的元素都必须实现Comparable接口。当插入元素时，PriorityBlockingQueue会使用CompareTo()方法来决定元素插入的位置，元素越大越靠后。PriorityBlockingQueue是一个阻塞式的数据结构。当它的方法被调用且不能立即执行时，调用这个方法的线程将被阻塞直到方法执行完成。

public class Event implements Comparable<Event> {
    private int thread;
    private int priority;
    public Event(int thread, int priority) {
        super();
        this.thread = thread;
        this.priority = priority;
    }
    public int getThread() {
        return thread;
    }
    public int getPriority() {
        return priority;
    }
    @Override
    public int compareTo(Event o) {
        if(this.priority>o.getPriority()){
            return -1;
        }else if(this.priority<o.getPriority()){
            return 1;
        }else{
            return 0;
        }
    }
}

public class Task implements Runnable {
    private int id;
    private PriorityBlockingQueue<Event> queue;
    public Task(int id, PriorityBlockingQueue<Event> queue) {
        super();
        this.id = id;
        this.queue = queue;
    }
    @Override
    public void run() {
        for (int i = 0; i < 100; i++) {
            Event event = new Event(id, i);
            queue.add(event);
        }
    }
}

public class PriorityBlockingQueueMain {
    public static void main(String[] args) {
        PriorityBlockingQueue<Event> queue = new PriorityBlockingQueue<Event>();
        Thread threads[] = new Thread[5];
        for (int i = 0; i < threads.length; i++) {
            Task task = new Task(i, queue);
            threads[i] = new Thread(task);
        }
        for (int i = 0; i < threads.length; i++) {
            threads[i].start();
        }
        for (int i = 0; i < threads.length; i++) {
            try {
                threads[i].join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        System.out.println("Main:Queue Size:" + queue.size());
        for (int i = 0; i < threads.length * 100; i++) {
            Event event = queue.poll();
            System.out.println("Thread "+ event.getThread()+" :Priority "+event.getPriority());
        }
        System.out.println("Main:Queue Size:" + queue.size());
        System.out.println("Main: End");
    }
}