【并发编程】- Semaphore-创建字符串池

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使用Semaphore创建字符串池

​ 类Semaphore可有效地对并发执行任务的线程数量进行限制，这种功能可应用在pool池技术中，可以设置同时访问pool池中数据的线程数量。

​ 同时有若干个线程可以访问池中的数据，但同时只有一个线程可以取得数据，使用完毕后再放回池中。

字符串池实现代码：

public class ListPool {

    private int poolMaxSize = 5;
    private int semaphorePermits=5;
    private List<String> list = new ArrayList<String>();
    private Semaphore semaphore = new Semaphore(semaphorePermits);
    private ReentrantLock reentrantLock = new ReentrantLock();
    private Condition condition = reentrantLock.newCondition();

    public ListPool(){
        super();
        for (int i = 0; i < poolMaxSize ; i++) {
            list.add("ozx"+(i+1));
        }
    }

    public String get(){
        String getValue = null;
        try {
            semaphore.acquire();
            reentrantLock.lock();
            while(list.size() == 0){
                condition.await();
            }
            getValue = list.remove(0);
            reentrantLock.unlock();
            semaphore.release();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return getValue;
    }

    public void put(String value){
        reentrantLock.lock();
        list.add(value);
        condition.signalAll();
        reentrantLock.unlock();
    }
}

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线程类代码：

@Slf4j
public class ListPoolThread implements Runnable {

    private ListPool listPool;

    public ListPoolThread(ListPool listPool){
        super();
        this.listPool=listPool;
    }


    @Override
    public void run() {
        for (int i = 0; i < Integer.MAX_VALUE ; i++) {
            String getValue = listPool.get();
            log.info("线程名：{} 获取的字符串的值：{}",Thread.currentThread().getName(),getValue);
            listPool.put(getValue);
        }
    }
}
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运行类代码如下：

public class ListPoolTest {
    public static void main(String[] args) {
        ListPool listPool = new ListPool();
        ListPoolThread[] poolThreads = new ListPoolThread[10];
        for (int i = 0; i < poolThreads.length ; i++) {
            poolThreads[i] = new ListPoolThread(listPool);
        }
        for (int i = 0; i < poolThreads.length ; i++) {
            new Thread(poolThreads[i]).start();
        }
    }
}
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运行结果如下：

17:26:28.111 [Thread-5] INFO com.ozx.concurrentprogram.semaphore.entity.ListPoolThread - 线程名：Thread-5 获取的字符串的值：ozx1
17:26:28.111 [Thread-2] INFO com.ozx.concurrentprogram.semaphore.entity.ListPoolThread - 线程名：Thread-2 获取的字符串的值：ozx2
17:26:28.111 [Thread-8] INFO com.ozx.concurrentprogram.semaphore.entity.ListPoolThread - 线程名：Thread-8 获取的字符串的值：ozx5
17:26:28.111 [Thread-7] INFO com.ozx.concurrentprogram.semaphore.entity.ListPoolThread - 线程名：Thread-7 获取的字符串的值：ozx4
17:26:28.111 [Thread-5] INFO com.ozx.concurrentprogram.semaphore.entity.ListPoolThread - 线程名：Thread-5 获取的字符串的值：ozx1
17:26:28.113 [Thread-5] INFO com.ozx.concurrentprogram.semaphore.entity.ListPoolThread - 线程名：Thread-5 获取的字符串的值：ozx1
17:26:28.113 [Thread-5] INFO com.ozx.concurrentprogram.semaphore.entity.ListPoolThread - 线程名：Thread-5 获取的字符串的值：ozx1
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