ReentrantReadWriterLock初步了解

ReentrantReadWriterLock初步了解

ReentrantReadWriter lock=new ReentrantReadWriter();

读锁建立：lock.readLock().lock(); 解除：lock.readLock().unlock();

写锁建立：lock.writeLock().lock(); 解除：lock.writeLock().unlock();

测试类：

//实体类   
class LockQueue {
        private Object data = null;
        private ReentrantReadWriteLock lock = new ReentrantReadWriteLock();

        public void get() {
            //上读锁
            lock.readLock().lock();
            System.out.println(Thread.currentThread().getName() + "准备好读取data");
            try {
                Thread.sleep((long) (Math.random() * 1000));
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                System.out.println(Thread.currentThread().getName() + "已经读取到了data");
                lock.readLock().unlock();
            }
        }

        public void put(Object data) {
            //上写锁
            lock.writeLock().lock();
            System.out.println(Thread.currentThread().getName() + "准备好写data!");
            try {
                Thread.sleep((long) (Math.random() * 1000));
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                this.data = data;
                System.out.println(Thread.currentThread().getName() + "已经写好了data!");
                lock.writeLock().unlock();
            }
        }
    }

用线程时候

    /**
     *@Author: wangshun
     *@date: 2022/8/9 16:04
     *@Description: 最后输出为：为正确的结果
     *
     * Thread-48准备好读取data
     * Thread-47准备好读取data
     * Thread-50准备好读取data
     * Thread-49准备好读取data
     * --------------------------- 这样的读锁是能够并行的，多线程并行
     * Thread-47已经读取到了data
     * Thread-48已经读取到了data
     * Thread-49已经读取到了data
     * Thread-50已经读取到了data
     * ---------------------------
     * Thread-51准备好写data!
     * Thread-51已经写好了data!-----这样的写锁是不能并行的，只能等上一个线程结束才能执行下一个线程
     *
     * Thread-52准备好写data!
     * Thread-52已经写好了data!
     *
     * Thread-53准备好写data!
     * Thread-53已经写好了data!
     *
     * Thread-54准备好写data!
     * Thread-54已经写好了data!
     *
     *@Version: 1.0
     */
    @ApiOperation("测试锁2")
    @PostMapping("/testLock2")
    public void testLockNew() {
        final LockQueue lock = new LockQueue();
        for (int i = 0; i < 4; ++i) {
            new Thread() {
                @Override
                public void run() {
                    //读锁测试
                    lock.get();
                }
            }.start();
        }

        for (int i = 0; i < 4; ++i) {
            new Thread() {
                @Override
                public void run() {
                    //写锁测试
                    lock.put(new Random().nextInt(10000));
                }
            }.start();
        }
    }

不用线程时候

    /**
     *@Author: wangshun
     *@date: 2022/8/9 16:06
     *@Description:
     *这里在上面的基础上进行修改，for循环中没用new Thread.start来启动，直接循环-->是有问题的
     *最后输出的都是一个线程，不是多线程了，而是单线程的多次循环
     *所以这里的读写锁不会起作用
     *这里的执行顺序就是单线程一步一步顺序进行的
     * http-nio-10003-exec-2准备好读取data
     * http-nio-10003-exec-2已经读取到了data
     * http-nio-10003-exec-2准备好读取data
     * http-nio-10003-exec-2已经读取到了data
     * http-nio-10003-exec-2准备好读取data
     * http-nio-10003-exec-2已经读取到了data
     * http-nio-10003-exec-2准备好读取data
     * http-nio-10003-exec-2已经读取到了data
     * http-nio-10003-exec-2准备好写data!
     * http-nio-10003-exec-2已经写好了data!
     * http-nio-10003-exec-2准备好写data!
     * http-nio-10003-exec-2已经写好了data!
     * http-nio-10003-exec-2准备好写data!
     * http-nio-10003-exec-2已经写好了data!
     * http-nio-10003-exec-2准备好写data!
     * http-nio-10003-exec-2已经写好了data!
     *@Version: 1.0
     */
    @PostMapping("/testLock3")
    @ApiOperation("读写锁测试3")
    public void testLock3() {
        StopWatch stopWatch = new StopWatch();
        stopWatch.start();
        LockQueue lockQueue = new LockQueue();
        for (int i = 0; i < 4; i++) {
            lockQueue.get();
        }

        for (int i = 0; i < 4; i++) {
            lockQueue.put("你好");
        }
        stopWatch.stop();
        System.out.println(stopWatch.prettyPrint());
    }