實踐作業的一種實現方式

strind發表於2024-10-20
package com.strind.jucdemo;

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

/**
 * @author strind
 * @date 2024/10/20 10:38
 * @description 作業
 */
public class ThirdLock implements Lock {
    private final Sync sync = new Sync(3);
    public static final class Sync extends AbstractQueuedSynchronizer{
        Sync(int count){
            if (count < 0){
                throw new IllegalArgumentException("同步狀態不得小於0");
            }
            setState(count);
        }

        @Override
        protected int tryAcquireShared(int arg) {
            while (true){
                int cur = getState();
                int lost = cur - arg;
                if (lost < 0 || compareAndSetState(cur,lost)){
                    return lost;
                }
            }
        }

        @Override
        protected boolean tryReleaseShared(int arg) {
            while (true){
                int cur = getState();
                int have = cur + arg;
                if (compareAndSetState(cur,have)){
                    return true;
                }
            }
        }
    }

    @Override
    public void lock(){
        sync.acquireShared(1);
    }

    @Override
    public void lockInterruptibly() throws InterruptedException {

    }

    @Override
    public boolean tryLock() {
        return false;
    }

    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return false;
    }

    @Override
    public void unlock() {
        sync.releaseShared(1);
    }

    @Override
    public Condition newCondition() {
        return null;
    }

}

package com.strind.jucdemo;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;

/**
 * @author strind
 * @date 2024/10/20 10:43
 * @description 測試類
 */
public class ThirdLockTest {


    public static void main(String[] args) throws InterruptedException {
        Lock lock = new ThirdLock();

        CountDownLatch latch = new CountDownLatch(10);
        class Worker extends Thread {

            @Override
            public void run() {
                while (true){
                    lock.lock();
                    try {
                        TimeUnit.SECONDS.sleep(2);
                        System.out.println("threadName ==> " + Thread.currentThread().getName());
                        TimeUnit.SECONDS.sleep(1);
                        latch.countDown();
                    } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                    }finally {
                        lock.unlock();
                    }
                }
            }
        }

        for (int i = 0; i < 10; i++) {
            Worker worker = new Worker();
            worker.start();
        }
        latch.await();
    }

}

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