定義 ? ?

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棧是Vector的一個子類，它實現(xiàn)了一個標(biāo)準(zhǔn)的后進(jìn)先出的棧。堆棧只定義了默認(rèn)構(gòu)造函數(shù)，用來創(chuàng)建一個空棧。 堆棧除了包括由Vector定義的所有方法，也定義了自己的一些方法。

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圖例 ? ? ? ? ? ?

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在下面圖片中可以看到進(jìn)棧（push）和出棧（pop）的過程。簡單來說，棧只有一個入口（出口），所以先進(jìn)后出（后進(jìn)先出）就不難理解。

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常用方法 ? ? ? ? ? ? ?

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序號	方法名	描述
1	Object?push()	把項壓入堆棧頂部
2	Object?pop()	移除堆棧頂部的對象，并作為此函數(shù)的值返回該對象
3	Object?peek()	查看堆棧頂部的對象，但不從堆棧中移除它。
4	boolean empty()	測試堆棧是否為空。
5	int search()	返回對象在堆棧中的位置，以 1 為基數(shù)。

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源碼

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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

?以上源碼摘自jdk1.8，如需下載jdk1.8官方文檔請點擊這里。

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

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轉(zhuǎn)載于:https://www.cnblogs.com/Y-zhiwei/p/8176554.html

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