java：aqs实现自定义锁

news2024/11/27 20:24:47

aqs采用模板方式设计模式，需要重写方法

package com.company.aqs;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

public class SelfLock implements Lock {
    // 静态内部类，自定义同步器
    private static class Sync extends AbstractQueuedSynchronizer {

        /**
         * 获取锁
         * @param arg
         * @return
         */
        @Override
        protected boolean tryAcquire(int arg) {
            if(compareAndSetState(0,1)){
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }else{
                return false;
            }
        }

        /**
         * 释放锁
         * @param arg
         * @return
         */
        @Override
        protected boolean tryRelease(int arg) {
            //判断是否是持有线程释放锁
            if(getExclusiveOwnerThread() != Thread.currentThread()){
                throw new RuntimeException();
            }
            if(getState() == 0){
                throw new RuntimeException();
            }
            //释放锁
            setExclusiveOwnerThread(null);
            setState(0);
            return true;
        }

        @Override
        protected boolean isHeldExclusively() {
            return  getState() == 1;
        }

        // 返回一个Condition，每个condition都包含了一个condition队列
        Condition newCondition() {
            return new ConditionObject();
        }

    }

    // 仅需要将操作代理到Sync上即可
    private final Sync sync = new Sync();

    public void lock() {
    	System.out.println(Thread.currentThread().getName()+" ready get lock");
        sync.acquire(1);
        System.out.println(Thread.currentThread().getName()+" already got lock");
    }

    public boolean tryLock() {
        return sync.tryAcquire(1);
    }

    public void unlock() {
    	System.out.println(Thread.currentThread().getName()+" ready release lock");
        sync.release(1);
        System.out.println(Thread.currentThread().getName()+" already released lock");
    }

    public Condition newCondition() {
        return sync.newCondition();
    }

    public boolean isLocked() {
        return sync.isHeldExclusively();
    }

    public boolean hasQueuedThreads() {
        return sync.hasQueuedThreads();
    }

    public void lockInterruptibly() throws InterruptedException {
        sync.acquireInterruptibly(1);
    }

    public boolean tryLock(long timeout, TimeUnit unit) throws InterruptedException {
        return sync.tryAcquireNanos(1, unit.toNanos(timeout));
    }
}

测试自定义显示锁

package com.company.aqs;


import com.company.SleepTools;

import java.util.concurrent.locks.Lock;

public class TestMyLock {

    public void test() {
        final Lock lock = new SelfLock();
        class Worker extends Thread {

			public void run() {
                lock.lock();
                System.out.println(Thread.currentThread().getName());
                try {
                    SleepTools.second(1);
                } finally {
                    lock.unlock();
                }
            }
        }
        // 启动4个子线程
        for (int i = 0; i < 3; i++) {
            Worker w = new Worker();
            //w.setDaemon(true);
            w.start();
        }
        // 主线程每隔1秒换行
        for (int i = 0; i < 10; i++) {
        	SleepTools.second(1);
            //System.out.println();
        }
    }

    public static void main(String[] args) {
        TestMyLock testMyLock = new TestMyLock();
        testMyLock.test();
    }
}