JAVA 之 栈

以下是自己实现的栈

• 栈 主要是 先进后出

• 栈（Stack）是一个后进先出（Last in first out,LIFO）的线性表，它要求只在表尾进行删除和插入操作。

Stack.png

---

package com.mylzs.cn.Utils;

import java.util.LinkedList;
![YWA)8LD)LC~(S~@@C]@VZ]K.png](https://img.haomeiwen.com/i2783497/ca88f65ad6b01928.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

/**
 * Created by zs on 17/11/8.
 *
 * 栈主要是 后进先出、抓住这个原理、就可以写了
 */
public class MyStack<S> {
  private LinkedList<S> linkedList=new LinkedList<S>();

    /**
     * 进栈
     * @param s
     */
   public void push(S s){
        linkedList.offerFirst(s);
   }

    /**
     * 得到栈顶
     * @return
     */
   public S peek(){
     return   linkedList.peekFirst();
   }

    /**
     * 出栈
     * @return
     */
   public S pop(){

       return  linkedList.pollFirst();
   }

    /**
     * 判断栈 是否为空!
     * @return
     */
   public Boolean isEmpty(){
       return  linkedList.isEmpty();
   }

   
}

---

• 栈的运行代码

    public static void main(String[] args) {
        MyStack<String> myStack=new MyStack<>();
        String str="我 和 你";
        System.out.print("进栈之前:");
        System.out.println(str);
        for (String s :
                str.split(" ")) {
            myStack.push(s);
        }
        System.out.print("出栈之后:");
        while (!myStack.isEmpty())
            System.out.print(myStack.pop()+" ");

    }

---

-运行结果图

结果

---

• java Stack源码

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;
}

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