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<title>csdn_编写一个JAVA的队列类</title>
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<td WIDTH="50%" bordercolor="#FFFFFF" CLASS="t1" bgcolor="#F0F0F0" align="center" nowrap>编写一个JAVA的队列类 </td>
<p> <td WIDTH="50%" bordercolor="#FFFFFF" CLASS="t1" bgcolor="#F0F0F0" align="center" nowrap>作者：梁颖健</td></p>
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<p align="left"> 队列是设计程序中常用的一种数据结构。它类似日常生活中的排队现象，采用一种被称为“先进先出”(LIFO)的存储结构。数据元素只能从队尾进入，从队首取出。在队列中，数据元素可以任意增减，但数据元素的次序不会改变。每当有数据元素从队列中被取出，后面的数据元素依次向前移动一位。所以，任何时候从队列中读到的都是队首的数据。<br>
根据这些特点，对队列定义了以下六种操作：<br>
enq(x) 向队列插入一个值为x的元素；<br>
deq() 从队列删除一个元素；<br>
front() 从队列中读一个元素，但队列保持不变；<br>
empty() 判断队列是否为空，空则返回真；<br>
clear() 清空队列；<br>
search(x) 查找距队首最近的元素的位置，若不存在，返回-1。<br>
<br>
Vector类是JAVA中专门负责处理对象元素有序存储和任意增删的类，因此，用Vector可以快速实现JAVA的队列类。<br>
<br>
public class Queue extends java.util.Vector {<br>
public Queue() {<br>
super();<br>
} <br>
public synchronized void enq(Object x) {<br>
super.addElement(x);<br>
} <br>
public synchronized Object deq() {<br>
/* 队列若为空，引发EmptyQueueException异常 */<br>
if( this.empty() )<br>
throw new EmptyQueueException();<br>
Object x = super.elementAt(0);<br>
super.removeElementAt(0);<br>
return x;<br>
} <br>
public synchronized Object front() {<br>
if( this.empty() )<br>
throw new EmptyQueueException();<br>
return super.elementAt(0);<br>
} <br>
public boolean empty() {<br>
return super.isEmpty();<br>
}<br>
public synchronized void clear() {<br>
super.removeAllElements();<br>
} <br>
public int search(Object x) {<br>
return super.indexOf(x);<br>
} <br>
}<br>
<br>
public class EmptyQueueException extends java.lang.RuntimeException {<br>
public EmptyQueueException() {<br>
super();<br>
} <br>
}<br>
<br>
以上程序在JDK1.1.5下编译通过
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