public class SynchronizedClass {
  public synchronized void syncMethod(){
    //代码
  }

  public void syncThis(){
    synchronized (this){
      //代码
    }
  }

  public void syncClassMethod(){
    synchronized (SynchronizedClass.class){
      //代码
    }
  }

  public synchronized static void syncStaticMethod(){
    //代码
  }
}

public class ReentrantLockDemo {
  Lock lock = new ReentrantLock();

  public void doSth(){
    lock.lock();
    try {
      //执行某些操作
    }finally {
      lock.unlock();
    }
  }
}

public class MyArrayBlockingQueue<T> {

//  数据数组
  private final T[] items;

  private final Lock lock = new ReentrantLock();

  private Condition notFull = lock.newCondition();
  private Condition notEmpty = lock.newCondition() ;

//  头部索引
  private int head;
//  尾部索引
  private int tail ;
//  数据的个数
  private int count;

  public MyArrayBlockingQueue(int maxSize) {
    items = (T[]) new Object[maxSize];
  }

  public MyArrayBlockingQueue(){
    this(10);
  }

  public void put(T t){
    lock.lock();
    try {
      while(count == getCapacity()){
        System.out.println("数据已满，等待");
        notFull.await();
      }
      items[tail] =t ;
      if(++tail ==getCapacity()){
        tail = 0;
      }
      ++count;
      notEmpty.signalAll();//唤醒等待数据的线程
    } catch (InterruptedException e) {
      e.printStackTrace();
    }finally {
      lock.unlock();
    }
  }

  public int getCapacity(){
    return items.length ;
  }

  public T take(){
    lock.lock();
    try {
      while(count ==0){
        System.out.println("还没有数据，等待");
        //哪个线程调用await()则阻塞哪个线程
        notEmpty.await();
      }
      T ret = items[head];
      items[head] = null ;
      if(++head == getCapacity()){
        head =0 ;
      }
      --count;
      notFull.signalAll();
      return ret ;
    } catch (InterruptedException e) {
      e.printStackTrace();
    }finally {
      lock.unlock();
    }
    return null ;
  }

  public int size(){
    lock.lock();
    try {
      return count;
    }finally {
      lock.unlock();
    }
  }

  public static void main(String[] args){
    MyArrayBlockingQueue<Integer> aQueue = new MyArrayBlockingQueue<>();
    aQueue.put(3);
    aQueue.put(24);
    for(int i=0;i<5;i++){
      System.out.println(aQueue.take());
    }

    System.out.println("结束");
  }
}

public class SemaphoreTest {
  public static void main(String[] args){
    final ExecutorService executorService = Executors.newFixedThreadPool(3);
    final Semaphore semaphore = new Semaphore(3);
    List<Future> futures = new ArrayList<>();
    for (int i = 0; i < 5; i++) {
      Future<?> submit = executorService.submit(new Runnable() {
        @Override
        public void run() {
          try {
            semaphore.acquire();
            System.out.println(" 剩余许可: " + semaphore.availablePermits());
            Thread.sleep(3000);
            semaphore.release();
          } catch (InterruptedException e) {
            e.printStackTrace();
          }
        }
      });
      futures.add(submit);
    }
  }
}