我写的一个堆栈程序

//创建堆栈节点类




class StackElement...{


int data;　//存放数据


StackElement nextElement; //指下一节点的指针






StackElement(int data)...{


this.data=data;


this.nextElement=null;


}




public int Value()...{


return data;


}


}




//创建堆栈类




class Stack...{


StackElement top; //栈顶指针




Stack()...{


top=null;


}




public void push(int data)...{




if (top==null)...{


top=new StackElement(data);


top.nextElement=null;


return;


}


StackElement temp=new StackElement(data);


temp.nextElement=top;


top=temp;


}




public int pop()...{




if (top==null)...{


return -1;


}


int temp=top.Value();


top=top.nextElement;


return temp;


}




public boolean isEmpty()...{


return top==null;


}


}




//创建堆栈实例




public class StackDemo...{




public static void main(String[] args)...{


Stack q=new Stack();




int[] intArray=...{31, 53, 8, 21, 9, 23};




for(int i=0; i<intArray.length; i++)...{


q.push(intArray[i]);


}


System.out.print("the Elements of the Stack q: ");




while(!q.isEmpty())...{


System.out.print(q.pop()+" ");


}


System.out.println();


}


}



今天 看到了JAVA定义的堆栈类Stack的源代码特来更新下，如下：




/**//*


* @(#)Stack.java 1.28 03/12/19


*


* Copyright 2004 Sun Microsystems, Inc. All rights reserved.


* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.


*/




package java.util;






/** *//**


* The <code>Stack</code> class represents a last-in-first-out


* (LIFO) stack of objects. It extends class <tt>Vector</tt> with five


* operations that allow a vector to be treated as a stack. The usual


* <tt>push</tt> and <tt>pop</tt> operations are provided, as well as a


* method to <tt>peek</tt> at the top item on the stack, a method to test


* for whether the stack is <tt>empty</tt>, and a method to <tt>search</tt>


* the stack for an item and discover how far it is from the top.


* <p>


* When a stack is first created, it contains no items.


*


* @author Jonathan Payne


* @version 1.28, 12/19/03


* @since JDK1.0


*/


public




class Stack<E> extends Vector<E> ...{




/** *//**


* Creates an empty Stack.


*/




public Stack() ...{


}






/** *//**


* Pushes an item onto the top of this stack. This has exactly


* the same effect as:


* <blockquote><pre>


* addElement(item)</pre></blockquote>


*


* @param item the item to be pushed onto this stack.


* @return the <code>item</code> argument.


* @see java.util.Vector#addElement


*/




public E push(E item) ...{


addElement(item);




return item;


}






/** *//**


* Removes the object at the top of this stack and returns that


* object as the value of this function.


*


* @return The object at the top of this stack (the last item


* of the <tt>Vector</tt> object).


* @exception EmptyStackException if this stack is empty.


*/




public synchronized E pop() ...{


E obj;


int len = size();




obj = peek();


removeElementAt(len - 1);




return obj;


}






/** *//**


* Looks at the object at the top of this stack without removing it


* from the stack.


*


* @return the object at the top of this stack (the last item


* of the <tt>Vector</tt> object).


* @exception EmptyStackException if this stack is empty.


*/




public synchronized E peek() ...{


int len = size();




if (len == 0)


throw new EmptyStackException();


return elementAt(len - 1);


}






/** *//**


* Tests if this stack is empty.


*


* @return <code>true</code> if and only if this stack contains


* no items; <code>false</code> otherwise.


*/




public boolean empty() ...{


return size() == 0;


}






/** *//**


* Returns the 1-based position where an object is on this stack.


* If the object <tt>o</tt> occurs as an item in this stack, this


* method returns the distance from the top of the stack of the


* occurrence nearest the top of the stack; the topmost item on the


* stack is considered to be at distance <tt>1</tt>. The <tt>equals</tt>


* method is used to compare <tt>o</tt> to the


* items in this stack.


*


* @param o the desired object.


* @return the 1-based position from the top of the stack where


* the object is located; the return value <code>-1</code>


* indicates that the object is not on the stack.


*/




public synchronized int search(Object o) ...{


int i = lastIndexOf(o);






if (i >= 0) ...{


return size() - i;


}


return -1;


}






/** *//** use serialVersionUID from JDK 1.0.2 for interoperability */


private static final long serialVersionUID = 1224463164541339165L;


}