Java Blocking Queue 實作範例

import java.util.concurrent.locks.*;

public class ArrayBlockingQueue<T> {
  private final Lock lock = new ReentrantLock();
  private final Condition notFull = lock.newCondition();
  private final Condition notEmpty = lock.newCondition();
  private final Object[] items;
  private int putIndex;
  private int takeIndex;
  private int count;

  public ArrayBlockingQueue(int capacity) {
    if (capacity <= 0)
      throw new IllegalArgumentException("Capacity must be positive");
    items = new Object[capacity];
  }

  public void put(T item) throws InterruptedException {
    lock.lock();
    try {
      while (count == items.length) {
        notFull.await();
      }
      items[putIndex] = item;
      if (++putIndex == items.length) {
        putIndex = 0;
      }
      ++count;
      notEmpty.signal();
    } finally {
      lock.unlock();
    }
  }

  public T take() throws InterruptedException {
    lock.lock();
    try {
      while (count == 0) {
        notEmpty.await();
      }
      Object item = items[takeIndex];
      if (++takeIndex == items.length) {
        takeIndex = 0;
      }
      --count;
      notFull.signal();
      return (T) item;
    } finally {
      lock.unlock();
    }
  }
}