package bluej.utility;




| General purpose Queue class
|
| $Id: Queue.java 6215 2009-03-30 13:28:25Z polle $
|
public class Queue
{       
private Elem head;
   
   private Elem tail;  
   
   public Queue()
   { 
      head = null;

      tail = null;     
      }  
   
   public synchronized void enqueue(Object data)
   {
      if (tail == null)
	   
      head = tail = new Elem(data);

      else
	   { 	
         tail.next = new Elem(data);
	
         tail = tail.next; 	    
         }     
      }  
   
   public synchronized Object dequeue()
   { 
      Object ret = null;
		
      if (head != null)
	   { 	
         ret = head.data;
	
         head = head.next;
         if (head == null)
		   
         tail = null; 	    
         }
		

      return ret;     
      }  
   
   public synchronized boolean isEmpty()
   { 
      return tail == null;     
      }  
   
   class Elem
{       
Object data;

      Elem next;  
      Elem(Object data)
{              
this.data = data;
	   
         this.next = null; 
         }     
      } 
   }