Semaphore semaphore = new Semaphore(10,true);
semaphore.acquire();
//do something here
semaphore.release();

public class ResourceManage { 
  private final Semaphore semaphore ; 
  private boolean resourceArray[]; 
  private final ReentrantLock lock; 
  public ResourceManage() { 
    this.resourceArray = new boolean[10];//存放厕所状态 
    this.semaphore = new Semaphore(10,true);//控制10个共享资源的使用，使用先进先出的公平模式进行共享;公平模式的信号量，先来的先获得信号量 
    this.lock = new ReentrantLock(true);//公平模式的锁，先来的先选 
    for(int i=0 ;i<10; i++){ 
      resourceArray[i] = true;//初始化为资源可用的情况 
    } 
  } 
  public void useResource(int userId){ 
 semaphore.acquire(); 
    try{ 
      //semaphore.acquire(); 
      int id = getResourceId();//占到一个坑 
      System.out.print("userId:"+userId+"正在使用资源，资源id:"+id+"\n"); 
      Thread.sleep(100);//do something，相当于于使用资源 
      resourceArray[id] = true;//退出这个坑 
    }catch (InterruptedException e){ 
      e.printStackTrace(); 
    }finally { 
      semaphore.release();//释放信号量，计数器加1 
    } 
  } 
  private int getResourceId(){ 
    int id = -1; 
 lock.lock();
    try { 
      //lock.lock();//虽然使用了锁控制同步，但由于只是简单的一个数组遍历，效率还是很高的，所以基本不影响性能。 
      for(int i=0; i<10; i++){ 
        if(resourceArray[i]){ 
          resourceArray[i] = false; 
          id = i; 
          break; 
        } 
      } 
    }catch (Exception e){ 
      e.printStackTrace(); 
    }finally { 
      lock.unlock(); 
    } 
    return id; 
  } 
} 
public class ResourceUser implements Runnable{ 
  private ResourceManage resourceManage; 
  private int userId; 
  public ResourceUser(ResourceManage resourceManage, int userId) { 
    this.resourceManage = resourceManage; 
    this.userId = userId; 
  } 
  public void run(){ 
    System.out.print("userId:"+userId+"准备使用资源...\n"); 
    resourceManage.useResource(userId); 
    System.out.print("userId:"+userId+"使用资源完毕...\n"); 
  } 
  
  public static void main(String[] args){ 
    ResourceManage resourceManage = new ResourceManage(); 
    Thread[] threads = new Thread[100]; 
    for (int i = 0; i < 100; i++) { 
      Thread thread = new Thread(new ResourceUser(resourceManage,i));//创建多个资源使用者 
      threads[i] = thread; 
    } 
    for(int i = 0; i < 100; i++){ 
      Thread thread = threads[i]; 
      try { 
        thread.start();//启动线程 
      }catch (Exception e){ 
        e.printStackTrace(); 
      } 
    } 
  } 
}