/** Copyright (c) 1994, 2010, Oracle and/or its affiliates. All rights reserved.* ORACLE 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.** <p>A more complete and consistent set of LIFO stack operations is* provided by the {@link Deque} interface and its implementations, which* should be used in preference to this class.  For example:* <pre>   {@code*   Deque<Integer> stack = new ArrayDeque<Integer>();}</pre>** @author  Jonathan Payne* @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).* @throws  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).* @throws  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;
}java.util.Stack

 

　　　　①Pushes an item onto the top of this stack.

public E push(E item) {addElement(item);return item;}

　　　　从类的结构图可以看出,addElement是Stack父类Vector封装，用于一切其子类的封装。

 

　　　　　#Adds the specified component to the end of this vector

public synchronized void addElement(E obj) {modCount++;ensureCapacityHelper(elementCount + 1);elementData[elementCount++] = obj;}

 

　　　　②Removes the object at the top of this stack and returns the onject that object as the value of this function

public synchronized E pop() {E       obj;int     len = size();obj = peek();removeElementAt(len - 1);return obj;}

　　　　　同样，跟addElement一样removeElementAt存在Vector

 

　　　　　　　#Deletes the component at the specified index. 

public synchronized void removeElementAt(int index) {modCount++;if (index >= elementCount) {throw new ArrayIndexOutOfBoundsException(index + " >= " +elementCount);}else if (index < 0) {throw new ArrayIndexOutOfBoundsException(index);}int j = elementCount - index - 1;if (j > 0) {System.arraycopy(elementData, index + 1, elementData, index, j);}elementCount--;elementData[elementCount] = null; /* to let gc do its work */}

　　　　　But,这个是什么 peek（），别慌它也是存在Stack类中下面我们讲这个

 

　　　　③Looks at the object at the top of this stack without remocing it

public synchronized E peek() {int     len = size();if (len == 0)throw new EmptyStackException();return elementAt(len - 1);}

　　　　　　跟addElement,removeElementAt一样，elementAt存在Vector

 

　　　　　　　　#Returns the component at the specified index.

public synchronized E elementAt(int index) {if (index >= elementCount) {throw new ArrayIndexOutOfBoundsException(index + " >= " + elementCount);}return elementData(index);}

 

　　　④Tests if this stack is empty 

public boolean empty() {return size() == 0;}

　　　　size() 来源于Vector,用于获取大小

 

　　　⑤Stack中其他，就不做介绍罗列下

　　　　void　Stack()　　//create an empty stackint　search(Object o)　　//return the 1 - based position where an obj is on this stack

 

　　数组实现

 

package sedion.jeffli.bean;/*** qq 1928348753* blog http://www.cnblogs.com/Alandre/* @author Jeff Li*/
public class myS {       Object[] data; int maxSize;   int top;       public myS(int maxSize) {       this.maxSize = maxSize;       data = new Object[maxSize];       top = -1;       }       /*** 获取堆栈长度* @return 堆栈长度*/ public int getSize() { return maxSize; } /*** 返回栈中元素的个数* @return 栈中元素的个数*/ public int getElementCount() { return top; } /*** 判断栈空* @return 栈空*/ public boolean isEmpty() { return top == -1; } /*** 判断栈满* @return 栈满*/ public boolean isFull() { return top+1 == maxSize; } /**   * 依次加入数据   * @param data 加入的数据   * @return 添加是否成功   */       public boolean push(Object data) {       if(isFull())  {       System.out.println("栈已满!");       return false;       }       this.data[++top] = data;       return true;       }       /**   * 从栈中取出数据   * @return 取出的数据   */       public Object pop() throws Exception{       if(isEmpty())  {       throw new Exception("栈已空!");       }       return this.data[top--];       }       /*** 返回栈顶元素* @return*/ public Object peek() { return this.data[getElementCount()];   } public static void main(String[] args) throws Exception {       myS stack=new myS(1000);       stack.push(new String("1"));       stack.push(new String("2"));       stack.push(new String("3"));       stack.push(new String("4"));       stack.push(new String("5"));   System.out.println("栈顶元素"+stack.peek());  while(stack.top>=0)       {       System.out.println("Position["+stack.top+"]:"+stack.pop());       }              }       
}

 

 

栈的应用

　　　　四则运算，计算器编程。这些，我想原理才是重要的。