[Java算法分析与设计]顺序栈的实现

　　在程序的世界，栈的应用是相当广泛的。其后进先出的特性，我们可以应用到诸如计算、遍历、代码格式校对等各个方面。但是你知道栈的底层是怎么实现的吗？现在跟随本篇文章我们来一睹它的庐山真面目吧。

　　首先我们先定义Stack的接口如下：

package com.chen.arithmetic_test.stack_test;

/**
 * Created by ChenMP on 2017/7/4.
 */
public interface Stack {
    //入栈
    public void push(Object obj) throws Exception;
    //出栈
    public Object pop() throws Exception;
    //获得栈顶元素
    public Object getTop() throws Exception;
    //判断栈是否为空
    public boolean isEmpty();
}

　　接下来，我们看看它的实现类：

package com.chen.arithmetic_test.stack_test;

/**
 * Created by ChenMP on 2017/7/4.
 */
public class SequenceStack implements Stack {
    private Object[] stack; //底层数据结构设计为对象数组
    private int top; //栈顶位置标记
    private int maxSize; //最大长度

    public SequenceStack() {
        this.stack = new Object[10];// 默认栈的长度为10
        this.top = 0;
        this.maxSize = 10;
    }

    public SequenceStack(int maxSize) {
        this.stack = new Object[maxSize];// 默认栈的长度为10
        this.top = 0;
        this.maxSize = maxSize;
    }

    @Override
    public void push(Object obj) throws Exception {
        if(top == maxSize)
            throw new Exception("堆栈已满！");

        stack[top] = obj; //添加入栈顶位置
        top++;  //栈顶位置标记+1
    }

    @Override
    public Object pop() throws Exception {
        if (0 == top)
            throw new Exception("堆栈为空！");

        Object returnObj = stack[top]; //获取栈顶位置数据对象
        stack[top] = null; //将该位置置为null，避免内存泄漏
        top--; //栈顶位置标记-1
        return returnObj ;
    }

    @Override
    public Object getTop() throws Exception {
        if (0 == top)
            throw new Exception("堆栈为空！");

        return stack[top-1];
    }

    @Override
    public boolean isEmpty() {
        return top>0?false:true;
    }
}

　　来测试我们实现的顺序栈吧！

package com.chen.arithmetic_test.stack_test;

import java.util.Scanner;

/**
 * Created by ChenMP on 2017/7/4.
 */
public class TestStack {
    public static void main(String[] args) throws Exception {
        // TODO Auto-generated method stub
        SequenceStack stack = new SequenceStack(10);

        Scanner in = new Scanner(System.in);
        int temp;
        for(int i=0;i<10;i++)
        {
            System.out.println("请输入第"+(i+1)+"个整数：");
            temp = in.nextInt();
            stack.push(temp);
        }

        while(!stack.isEmpty())
        {
            System.out.println(stack.pop());
        }
    }
}

　　通过上面的代码，其实也可以很清晰的理解顺序栈的实现原理对不对？给自己点个赞~