技術標籤：java

package Stack;

public class Calculator {
    public static void main(String[] args) {
        String expression = "7*3+3*6-3+1";
        ArrayStack2 numberStack = new ArrayStack2(10);
        ArrayStack2 operStack = new ArrayStack2(10);

        int index = 0;
        int num1 =
 
 0;
        int num2 = 0;
        int oper = 0;
        int res = 0;
        char ch = ' '; //用於儲存掃描到的數字

        String keepNum = "";   //方便兩位數的運算，用以拼接字串

        while (true) {
            ch = expression.substring(index, index + 1).charAt(0);
            if (operStack.isOper(ch)) {
                if
 
 (!operStack.isEmpty()) {
                    if (operStack.priority(ch) <= operStack.priority(operStack.peek())) {
                        num1 = numberStack.pop();
                        num2 = numberStack.pop();
                        oper = operStack.pop();
                        res = numberStack.
 
cal(num1, num2, oper);
                        numberStack.push(res);
                        operStack.push(ch);
                    } else {
                        operStack.push(ch);
                    }
                } else {
                    operStack.push(ch);
                }
            } else {
                keepNum += ch;// 這個是字串的拼接
                if (index == expression.length() - 1) {
                    numberStack.push(Integer.parseInt(keepNum)); //直接呼叫包裝類的方法，轉變成Int型
                } else {
                    if (operStack.isOper(expression.substring(index + 1, index + 2).charAt(0))) {
                        numberStack.push(Integer.parseInt(keepNum));
                        keepNum = "";
                    }
                }
            }
            index++;
            if (index >= expression.length()) {
                break;
            }
        }
        while (true) {
            //如果符號棧為空，則計算到最後的結果, 數棧中只有一個數字【結果】
            if (operStack.isEmpty()) {
                break;
            }
            num1 = numberStack.pop();
            num2 = numberStack.pop();
            oper = operStack.pop();
            res = numberStack.cal(num1, num2, oper);
            numberStack.push(res);//入棧
        }
        //將數棧的最後數，pop出，就是結果
        int res2 = numberStack.pop();
        System.out.printf("表示式 %s = %d", expression, res2);
    }
}


class ArrayStack2 {
    private int maxSize;
    private int[] stack;
    private int top = -1;

    public ArrayStack2(int maxSize) {
        this.maxSize = maxSize;
        stack = new int[maxSize]; //這裡其實是覆蓋了之前的陣列長度
    }

    //判斷棧滿   是在ArrayStack內部的方法，所以可以直接呼叫內部的引數    只要有返回數就是有返回值的，這裡是布林數
    public boolean isFull() {
        return top == maxSize - 1;
    }

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

    //向棧中新增數  push
    public void push(int merber) {
        if (isFull()) {
            System.out.println("棧滿，新增失敗");
        } else {
            stack[++top] = merber;
        }
    }

    //棧中彈出數     當需要有返回值的時候，需要返回異常
    public int pop() {
        int temp;
        if (isEmpty()) {
            throw new RuntimeException("棧滿，彈出失敗");
        } else {
            temp = stack[top--];
            return temp;
        }
    }

    public void show() {
        if (isEmpty()) {
            System.out.println("棧空");
            return;
        } else {
            for (int i = 0; i < top; i++) {
                System.out.printf("  %d  ", stack[i]);
            }
        }
    }

    //有下面的這些函式的根本原因是：因為傳入的是字串，要把字串理解了
    //判斷運算子的優先順序
    public int priority(int oper) {
        if (oper == '*' || oper == '/') {
            return 1;
        } else if (oper == '+' || oper == '-') {
            return 0;
        } else {
            return -1;
        }
    }

    //判斷是不是一個運算子
    public boolean isOper(char val) {
        return val == '+' || val == '-' || val == '*' || val == '/';
    }

    public int peek() {
        return stack[top];
    }

    //計算的方法
    public int cal(int num1, int num2, int oper) {
        int res = 0;
        switch (oper) {
            case '+':
                res = num1 + num2;
                break;
            case '-':
                res = num1 - num2;
                break;
            case '*':
                res = num1 * num2;
                break;
            case '/':
                res = num1 / num2;
                break;
            default:
                break;
        }
        return res;
    }
}