Java阻塞队列的实现及应用

//阻塞队列BlockQueue
static class BlockQueue{
    //该队列用一个数组来实现，我们让此队列的最大容量为10
        private int[] items = new int[10];
        private int head = 0;
        private int tail = 0;
        private int size = 0;
        private Object locker =new Object();
        //入队
        public void put(int item) throws InterruptedException {
            synchronized(locker) {
                while (size == items.length) {
                    //入队时，若队满，阻塞
                    locker.wait();
                }
                items[tail++] = item;
                //如果到达末尾，重回队首（实现循环队列）
                if (tail >= items.length) {
                    tail = 0;
                }
                size++;
                locker.notify();
            }
        }
        //出队
        public int back() throws InterruptedException {
            int ret = 0;
            synchronized (locker) {
                while (size == 0) {
                    //出队时，若队空，阻塞
                    locker.wait();
                }
                ret = items[head++];
                if (head >= items.length) {
                    head = 0;
                }
                size--;
                locker.notify();
            }
            return ret;
        }
    }

public static void main(String[] args) throws InterruptedException {
        BlockQueue blockQueue = new BlockQueue();
        //生产者线程
        Thread produce = new Thread(){
            @Override
            public void run() {
                for(int i = 0;i<10000;++i){
                    try {
                        System.out.println("生产了:"+i);
                        blockQueue.put(i);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        };
        produce.start();
        //消费者线程
        Thread customer = new Thread(){
            @Override
            public void run() {
                while (true) {
                    try {
                        int res = blockQueue.back();
                        System.out.println("消费了：" + res);
                        //每次消费后等1秒，也就是生产的快，消费的慢
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        };
        customer.start();
        customer.join();
        produce.join();
    }

import java.util.Timer;
import java.util.TimerTask;
public class Test{
public static void main(String[] args) {
        Timer timer = new Timer();
        System.out.println("代码开始执行");
        timer.schedule(new TimerTask() {
            @Override
            public void run() {
                System.out.println("触发定时器");
            }
        },3000);
    }
}

//Task类用来描述任务，它继承Comparable接口是因为要将任务放到优先级阻塞队列中
    static class Task implements Comparable<Task>{
        //command表示这个任务是什么
        private Runnable command;
        //time是一个时间戳
        private long time;
        public Task(Runnable command,long time){
            this.command = command;
            this.time = System.currentTimeMillis()+time;
        }
        public void run(){
            command.run();
        }
        //因为要将Task任务放到优先级阻塞队列中，所以要重写compareTo方法，我们将时间短的任务放到队头
        @Override
        public int compareTo(Task o) {
            return (int)(this.time - o.time);
        }
    }

//Timer类中需要有一个定时器，还需要有一个schedule方法
    static class Timer{
        //使用优先级阻塞队列来放这些任务，这样才能把最接近时钟的任务放到队头，我们每次扫描队头任务就行了
        private PriorityBlockingQueue<Task> queue = new PriorityBlockingQueue<>();
        //locker用来解决忙等问题
        private Object locker = new Object();
        //构造方法中完成定时器功能
        public Timer(){
            //需要构造一个线程，来不断地扫描队头，来判断队头任务是否到点，也就是是否该开始执行了
            Thread t = new Thread(){
                @Override
                public void run() {
                    while(true){
                        //取出队首任务来判断是否到时间了
                        try {
                            Task task = queue.take();
                            long current = System.currentTimeMillis();
                            //当前时间戳小于时钟时间戳，表明时间还没到,那就等待
                            if (current < task.time){
                                queue.put(task);
                                synchronized (locker){
                                    locker.wait(task.time-current);
                                }
                            }else{
                                //否则时间到，开始执行任务
                                task.run();
                            }
                        } catch (InterruptedException e) {
                                e.printStackTrace();
                                break;
                            }
                        }
                    }
                };
            t.start();
            }
        //schedule方法的两个参数，command为任务，delay为一个时间差例如：3000(单位为毫秒)
        public void schedule(Runnable command,long delay){
            Task task = new Task(command,delay);
            queue.put(task);
            synchronized (locker){
                locker.notify();
            }
        }
    }

public static void main(String[] args) {
        System.out.println("程序启动");
        Timer timer = new Timer();
        timer.schedule(new Runnable() {
            @Override
            public void run() {
                System.out.println("触发定时器");
            }
        },3000);//3000表示定时时间为3秒
    }