實現一個自己的類ReentrantLock

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

/**
 *
 * 實現一個自己的類ReentrantLock
 */
public class SelfLock implements Lock {
    //state=1表示獲取到了鎖，state=0表示這個鎖當前沒有線程拿到
    private static class Sync extends AbstractQueuedSynchronizer {
        //是否佔用
        protected boolean isHeldExclusively() {
            return getState()==1;
        }
        protected boolean tryAcquire(int arg) {
            if(compareAndSetState(0,1)) {
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }
        protected boolean tryRelease(int arg) {
            if(getState()==0) {
                throw new UnsupportedOperationException();
            }
            setExclusiveOwnerThread(null);
            setState(0);
            return true;
        }
        Condition newCondition() {
            return new ConditionObject();
        }
    }

    private final Sync sycn = new Sync();

    @Override
    public void lock() {
        sycn.acquire(1);

    }

    @Override
    public void lockInterruptibly() throws InterruptedException {
        sycn.acquireInterruptibly(1);

    }

    @Override
    public boolean tryLock() {
        return sycn.tryAcquire(1);
    }

    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return sycn.tryAcquireNanos(1, unit.toNanos(time));
    }

    @Override
    public void unlock() {
        sycn.release(1);

    }

    @Override
    public Condition newCondition() {
        return sycn.newCondition();
    }
}

 

import java.util.concurrent.TimeUnit;

/**
 * 線程休眠輔助工具類
 */
public class SleepTools {
    /**
     * 按秒休眠
     * @param seconds 秒數
     */
    public  static final void second(int seconds){
        try {
            TimeUnit.SECONDS.sleep(seconds);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    /**
     * 按毫秒數休眠
     * @param millis 毫秒數
     */
    public static final void milli(int millis){
        try {
            TimeUnit.MILLISECONDS.sleep(millis);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

 

/**
 *
 * 測試類似ReentrantLock的鎖
 */
public class TestMyLock {
    public void test() {
        final Lock lock = new SelfLock();
        
        class Worker extends Thread {
            public void run() {
                while (true) {
                    lock.lock();
                    try {
                       SleepTools.second(1);
                        System.out.println(Thread.currentThread().getName());
                        SleepTools.second(1);
                    } finally {
                        lock.unlock();
                    }
                    SleepTools.second(2);
                }
            }
        }
        // 啓動10個子線程
        for (int i = 0; i < 10; i++) {
            Worker w = new Worker();
            w.setDaemon(true);
            w.start();
        }
        // 主線程每隔1秒換行
        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();
    }
}