lqueue.java

基于图形的二叉树工作演示程序

package myBag;
import myBag.*;
public class LQueue{
   private  Link  front;  //指向首结点
   private  Link  rear;   //指向首结点

   public LQueue(){ setup(); }
   public LQueue(int sz){ setup(); }

   public void  setup(){
      front = rear = null;
   }

   public void clear(){ front = rear = null; }

   public void enqueue(Object  it){
      if(rear != null) {
         rear.setNext(new Link(it,null));
         rear = rear.next();
      }
      else  front = rear = new Link(it, null);
   }

   public Object  dequeue(){
      Assert.notFalse(! isEmpty(),"空队列");
      Object  it = front.element();
      front = front.next();
      if(front == null) rear = null;
      return  it;
   }

   public Object firstValue(){
      Assert.notFalse(! isEmpty(),"空队列");
      return  front.element();
   }

   public  boolean  isEmpty(){ return  front == null; }
}//class  LQueue