/**
 * @author 興趣使然黃小黃
 * @version 1.0
 * 用數(shù)組去模擬棧
 */
@SuppressWarnings({"all"})
public class ArrayStack {
    private int maxSize; //棧的大小
    private int[] stack; //用數(shù)組模擬棧
    private int top = -1; //指向棧頂

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

    //判斷棧滿
    public boolean isFull(){
        return top == maxSize - 1;
    }

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

    //入棧
    public void push(int value){
        //判斷是否滿
        if (isFull()){
            System.out.println("棧已滿，無法入棧!");
            return;
        }
        //入棧操作
        stack[++top] = value;
    }

    //出棧
    public int pop(){
        //先判斷是否為空
        if (isEmpty()){
            throw new RuntimeException("當(dāng)前棧已空，無法出棧!");
        }
        //出棧操作
        int value = stack[top];
        top--;
        return value;
    }

    //遍歷
    public void showStack(){
        //從棧頂開始遍歷
        if (isEmpty()){
            System.out.println("?？?);
        }
        for (int i = top; i >= 0; i--){
            System.out.printf("stack[%d] = %d\n", i, stack[i]);
        }
    }
}

import java.util.Scanner;

/**
 * @author 興趣使然黃小黃
 * @version 1.0
 * 測試棧
 */
@SuppressWarnings({"all"})
public class ArrayStackDemo {

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

        while (loop){
            System.out.println("show 顯示棧");
            System.out.println("exit 退出棧");
            System.out.println("pop 出棧");
            System.out.println("push 入棧");
            System.out.println("請輸入:");
            key = scanner.next();
            switch (key){
                case "show":
                    arrayStack.showStack();
                    break;
                case "exit":
                    scanner.close();
                    loop = false;
                    break;
                case "push":
                    System.out.println("請輸入要存入的值: ");
                    int value = scanner.nextInt();
                    arrayStack.push(value);
                    break;
                case "pop":
                    try {
                        System.out.println(arrayStack.pop() + "出棧");
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    break;
                default:
                    System.out.println("輸入有誤，請重新輸入！");
                    break;
            }
        }
        System.out.println("程序結(jié)束...");
    }
}

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

/**
 * @author 興趣使然黃小黃
 * @version 1.0
 * 簡單計算器實現(xiàn)
 */
@SuppressWarnings({"all"})
public class Calculator {

    public static void main(String[] args) {
        //接收表達式
        System.out.println("請輸入表達式: ");
        Scanner scanner = new Scanner(System.in);
        String expression = scanner.next();
        //創(chuàng)建一個數(shù)棧 一個符號棧
        Stack<Integer> numStack = new Stack<>();
        Stack<Integer> operStack = new Stack<>();
        //定義變量
        int index = 0; //用于掃描
        int num1 = 0;
        int num2 = 0;
        int oper = 0;
        int res = 0;
        char ch = ' '; //每次掃描的char保存
        String keepNum = ""; //用于保存多位數(shù)字進行拼接
        //掃描計算
        while (true){
            //依次得到expression每一個字符
            ch = expression.substring(index, index+1).charAt(0);
            //判斷ch進行相應(yīng)的處理
            if (isOper(ch)){
                //如果是運算符
                if (operStack.isEmpty()){
                    //判斷當(dāng)前的符號棧是否為空，若為空直接入棧
                    operStack.push((int)ch);
                }else {
                    //符號棧不為空
                    //若當(dāng)前操作符優(yōu)先級小于等于棧中的操作符
                    if (priority(ch) <= priority(operStack.peek())){
                        num1 = numStack.pop();
                        num2 = numStack.pop();
                        oper = operStack.pop();
                        res = cal(num1, num2, oper);
                        //將運算結(jié)果入數(shù)棧
                        numStack.push(res);
                        //將當(dāng)前的操作符入符號棧
                        operStack.push((int) ch);
                    }else {
                        operStack.push((int) ch);
                    }
                }
            }else {
                //如果是數(shù)字直接入數(shù)棧
                //需要考慮多位數(shù)的情況
                //如果當(dāng)前位置為數(shù)字，則繼續(xù)向后看，直到為符號或者遍歷完成為止
                //已經(jīng)查看的數(shù)字進行字符串拼接，即為正確的數(shù)字
                keepNum += ch;
                //如果已經(jīng)到末尾，則直接入棧
                if (index == expression.length()-1){
                    numStack.push(Integer.parseInt(keepNum));
                }else {
                    //判斷下一個字符是否為數(shù)字,若是則繼續(xù)掃描，不是則直接入棧
                    if (isOper(expression.substring(index+1, index+2).charAt(0))){
                        numStack.push(Integer.parseInt(keepNum)); //1的ascII碼為49，而ch為字符
                        keepNum = "";
                    }
                }
            }
            //index+1 并判斷是否掃描完畢
            index++;
            if (index >= expression.length()){
                break;
            }
        }

        //表達式掃描完畢過后，順序的從數(shù)棧和符號棧取出對應(yīng)的數(shù)字和符號進行運算
        //最后數(shù)棧只剩的一個數(shù)字為結(jié)果
        //也可以判斷符號棧是否為空，如果為空則說明數(shù)棧只剩一個數(shù)
        while (numStack.size() > 1){
            num1 = numStack.pop();
            num2 = numStack.pop();
            oper = operStack.pop();
            res = cal(num1, num2, oper);
            numStack.push(res);
        }
        //打印結(jié)果
        System.out.println("結(jié)果: " + numStack.pop());
    }

    //返回運算符號的優(yōu)先級，返回數(shù)字越大，優(yōu)先級越大
    public static int priority(int operation){
        if (operation == '*' || operation == '/'){
            return 1;
        }else if (operation == '+' || operation == '-'){
            return 0;
        }else {
            return -1;
        }
    }

    //判斷是否為運算符
    public static boolean isOper(char val){
        return val == '+' || val == '-' || val == '/' || val == '*';
    }

    //計算方法
    public static int cal(int num1, int num2, int operation){
        int res = 0; //存放返回的結(jié)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;
    }
}