数据结构——Java Stack 类

定义    

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栈是Vector的一个子类，它实现了一个标准的后进先出的栈。堆栈只定义了默认构造函数，用来创建一个空栈。 堆栈除了包括由Vector定义的所有方法，也定义了自己的一些方法。

 

图例            

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在下面图片中可以看到进栈（push）和出栈（pop）的过程。简单来说，栈只有一个入口（出口），所以先进后出（后进先出）就不难理解。

 

常用方法              

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序号	方法名	描述
1	Object push()	把项压入堆栈顶部
2	Object pop()	移除堆栈顶部的对象，并作为此函数的值返回该对象
3	Object peek()	查看堆栈顶部的对象，但不从堆栈中移除它。
4	boolean empty()	测试堆栈是否为空。
5	int search()	返回对象在堆栈中的位置，以 1 为基数。

 

源码

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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; } View Code

 以上源码摘自jdk1.8，如需下载jdk1.8官方文档请点击这里。

 

 

参考：http://www.runoob.com/java/java-stack-class.html　　https://www.cnblogs.com/leefreeman/archive/2013/05/16/3082400.html

 

转载于:https://www.cnblogs.com/Y-zhiwei/p/8176554.html

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