queue.java

Java程序设计技巧与开发实例附书源代码。

public class Queue
{
  private List customers = new List();

  private synchronized Object performAction(String cmd, Object obj)
  {
    if (cmd.equals("insert"))
    {
      if (!customers.isFull())
      {
        customers.add(obj);
      }
      notify();
      return null;
    }
    else if (cmd.equals("size"))
    {
      return new Integer(customers.getSize());
    }
    else if (cmd.equals("retrieve"))
    {
      while (customers.getSize() == 0)
      {
        try
        {
          wait();
        }
        catch (InterruptedException ie)
        {
          System.out.println("Synch error in queue: " + ie);
        }
      }
      Customer c = (Customer) customers.get(0);
      customers.delete(0);
      return c;
    }
    else
    {
      return null;
    }
  }

  public void insert(Customer c)
  {
    performAction("insert", c);
  }

  public int getSize()
  {
    return ( (Integer) performAction("size", null)).intValue();
  }

  public Customer requestCustomer()
  {
    return (Customer) performAction("retrieve", null);
  }
}