Java数据结构之栈与综合计算器的实现

@SuppressWarnings({"all"})
public class ArrayStack {
    private int maxSize; //栈的大小
    private int[] stack; //用数组模拟栈
    private int top = -1; //指向栈顶

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

    //判断栈满
    public boolean isFull(){
        return top == maxSize - 1;
    }

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

    //入栈
    public void push(int value){
        //判断是否满
        if (isFull()){
            System.out.println("栈已满，无法入栈!");
            return;
        }
        //入栈操作
        stack[++top] = value;
    }

    //出栈
    public int pop(){
        //先判断是否为空
        if (isEmpty()){
            throw new RuntimeException("当前栈已空，无法出栈!");
        }
        //出栈操作
        int value = stack[top];
        top--;
        return value;
    }

    //遍历
    public void showStack(){
        //从栈顶开始遍历
        if (isEmpty()){
            System.out.println("栈空");
        }
        for (int i = top; i >= 0; i--){
            System.out.printf("stack[%d] = %d\n", i, stack[i]);
        }
    }
}

import java.util.Scanner;


@SuppressWarnings({"all"})
public class ArrayStackDemo {

    public static void main(String[] args) {
        ArrayStack arrayStack = new ArrayStack(4);
        String key = "";
        boolean loop = true; //控制菜单
        Scanner scanner = new Scanner(System.in);

        while (loop){
            System.out.println("show 显示栈");
            System.out.println("exit 退出栈");
            System.out.println("pop 出栈");
            System.out.println("push 入栈");
            System.out.println("请输入:");
            key = scanner.next();
            switch (key){
                case "show":
                    arrayStack.showStack();
                    break;
                case "exit":
                    scanner.close();
                    loop = false;
                    break;
                case "push":
                    System.out.println("请输入要存入的值: ");
                    int value = scanner.nextInt();
                    arrayStack.push(value);
                    break;
                case "pop":
                    try {
                        System.out.println(arrayStack.pop() + "出栈");
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    break;
                default:
                    System.out.println("输入有误，请重新输入！");
                    break;
            }
        }
        System.out.println("程序结束...");
    }
}

import java.util.Scanner;
import java.util.Stack;


@SuppressWarnings({"all"})
public class Calculator {

    public static void main(String[] args) {
        //接收表达式
        System.out.println("请输入表达式: ");
        Scanner scanner = new Scanner(System.in);
        String expression = scanner.next();
        //创建一个数栈 一个符号栈
        Stack<Integer> numStack = new Stack<>();
        Stack<Integer> operStack = new Stack<>();
        //定义变量
        int index = 0; //用于扫描
        int num1 = 0;
        int num2 = 0;
        int oper = 0;
        int res = 0;
        char ch = ' '; //每次扫描的char保存
        String keepNum = ""; //用于保存多位数字进行拼接
        //扫描计算
        while (true){
            //依次得到expression每一个字符
            ch = expression.substring(index, index+1).charAt(0);
            //判断ch进行相应的处理
            if (isOper(ch)){
                //如果是运算符
                if (operStack.isEmpty()){
                    //判断当前的符号栈是否为空，若为空直接入栈
                    operStack.push((int)ch);
                }else {
                    //符号栈不为空
                    //若当前操作符优先级小于等于栈中的操作符
                    if (priority(ch) <= priority(operStack.peek())){
                        num1 = numStack.pop();
                        num2 = numStack.pop();
                        oper = operStack.pop();
                        res = cal(num1, num2, oper);
                        //将运算结果入数栈
                        numStack.push(res);
                        //将当前的操作符入符号栈
                        operStack.push((int) ch);
                    }else {
                        operStack.push((int) ch);
                    }
                }
            }else {
                //如果是数字直接入数栈
                //需要考虑多位数的情况
                //如果当前位置为数字，则继续向后看，直到为符号或者遍历完成为止
                //已经查看的数字进行字符串拼接，即为正确的数字
                keepNum += ch;
                //如果已经到末尾，则直接入栈
                if (index == expression.length()-1){
                    numStack.push(Integer.parseInt(keepNum));
                }else {
                    //判断下一个字符是否为数字,若是则继续扫描，不是则直接入栈
                    if (isOper(expression.substring(index+1, index+2).charAt(0))){
                        numStack.push(Integer.parseInt(keepNum)); //1的ascII码为49，而ch为字符
                        keepNum = "";
                    }
                }
            }
            //index+1 并判断是否扫描完毕
            index++;
            if (index >= expression.length()){
                break;
            }
        }

        //表达式扫描完毕过后，顺序的从数栈和符号栈取出对应的数字和符号进行运算
        //最后数栈只剩的一个数字为结果
        //也可以判断符号栈是否为空，如果为空则说明数栈只剩一个数
        while (numStack.size() > 1){
            num1 = numStack.pop();
            num2 = numStack.pop();
            oper = operStack.pop();
            res = cal(num1, num2, oper);
            numStack.push(res);
        }
        //打印结果
        System.out.println("结果: " + numStack.pop());
    }

    //返回运算符号的优先级，返回数字越大，优先级越大
    public static int priority(int operation){
        if (operation == '*' || operation == '/'){
            return 1;
        }else if (operation == '+' || operation == '-'){
            return 0;
        }else {
            return -1;
        }
    }

    //判断是否为运算符
    public static boolean isOper(char val){
        return val == '+' || val == '-' || val == '/' || val == '*';
    }

    //计算方法
    public static int cal(int num1, int num2, int operation){
        int res = 0; //存放返回的结果
        switch (operation){
            case '+':
                res = num1 + num2;
                break;
            case '-':
                res = num2 - num1;
                break;
            case '*':
                res = num1 * num2;
                break;
            case '/':
                res = num2 / num1;
                break;
            default:
                break;
        }
        return res;
    }
}