用数组实现stack（栈）：先入后出

直接上代码了

package com.leolee.dataStructure.stack;

/**
 * @ClassName ArrayStack
 * @Description: 数组模拟栈
 * @Author LeoLee
 * @Date 2020/9/15
 * @Version V1.0
 **/
public class ArrayStack {

    private int maxSize;

    private int[] stack;//数组来模拟栈

    private int top = -1;//栈顶，初始化为-1

    public ArrayStack (int maxSize) {
        this.maxSize = maxSize;
        stack = new int[maxSize];
    }

    //栈满
    public boolean isFull () {

        return top == (maxSize - 1);
    }

    //栈空
    public boolean isEmpty () {
        return top == -1;
    }

    //入栈
    public void push (int value) {

        if (isFull()) {
            System.out.println("stack is full");
            return;
        }
        top++;
        stack[top] = value;
    }

    //出栈
    public int pop () {

        if (isEmpty()) {
            throw new NullPointerException("stack is empty");
        }

        int topValue = stack[top];
        top--;
        return topValue;
    }

    //由于栈先进后出的原则，由数组的末尾开始遍历
    public void showData () {

        if (isEmpty()) {
            System.out.println("stack is empty");
            return;
        }

        for (int i = top; i >= 0 ; i--) {
            System.out.printf("stack[%d]:%d\n", i, stack[i]);
        }
    }
}

public static void main(String[] args) {

    ArrayStack arrayStack = new ArrayStack(4);
    arrayStack.push(1);
    arrayStack.push(2);
    arrayStack.push(3);
    arrayStack.push(4);
    arrayStack.showData();
    System.out.println("-----------------------------");
    arrayStack.pop();
    arrayStack.pop();
    arrayStack.showData();
}