java字符串计算器

以下是一个Java字符串计算器的示例代码，它可以实现基本的加减乘除和括号运算：

import java.util.*;

public class StringCalculator {
    private static final Map<String, Integer> priorityMap = new HashMap<String, Integer>() {{
        put("+", 1);
        put("-", 1);
        put("*", 2);
        put("/", 2);
        put("%", 2);
        put("^", 3);
    }};

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入表达式：");
        String expression = scanner.nextLine();
        System.out.println("计算结果为：" + calculate(expression));
    }

    public static String calculate(String s) {
        List<String> arrayList = reversePolish.parse(s);
        Stack<String> stringStack = new Stack<>();
        for (int i = 0; i < arrayList.size(); i++) {
            String str = arrayList.get(i);
            if (str.equals("+") || str.equals("-") || str.equals("*") || str.equals("/") || str.equals("^") || str.equals("%")) {
                cal(stringStack, str);
            } else {
                stringStack.push(str);
            }
        }
        return stringStack.pop();
    }

    private static void cal(Stack<String> stack, String op) {
        String b = stack.pop();
        String a = stack.pop();
        String result = "";
        switch (op) {
            case "+":
                result = String.valueOf(Double.parseDouble(a) + Double.parseDouble(b));
                break;
            case "-":
                result = String.valueOf(Double.parseDouble(a) - Double.parseDouble(b));
                break;
            case "*":
                result = String.valueOf(Double.parseDouble(a) * Double.parseDouble(b));
                break;
            case "/":
                result = String.valueOf(Double.parseDouble(a) / Double.parseDouble(b));
                break;
            case "^":
                result = String.valueOf(Math.pow(Double.parseDouble(a), Double.parseDouble(b)));
                break;
            case "%":
                result = String.valueOf(Double.parseDouble(a) % Double.parseDouble(b));
                break;
        }
        stack.push(result);
    }

    private static class reversePolish {
        public static List<String> parse(String s) {
            List<String> arrayList = new ArrayList<>();
            Stack<String> stack = new Stack<>();
            int i = 0;
            while (i < s.length()) {
                char c = s.charAt(i);
                if (Character.isDigit(c) || c == '.') {
                    int j = i;
                    while (j < s.length() && (Character.isDigit(s.charAt(j)) || s.charAt(j) == '.')) {
                        j++;
                    }
                    arrayList.add(s.substring(i, j));
                    i = j;
                } else if (c == '(') {
                    stack.push("(");
                    i++;
                } else if (c == ')') {
                    while (!stack.peek().equals("(")) {
                        arrayList.add(stack.pop());
                    }
                    stack.pop();
                    i++;
                } else {
                    String op = String.valueOf(c);
                    while (!stack.isEmpty() && !stack.peek().equals("(") && priorityMap.get(op) <= priorityMap.get(stack.peek())) {
                        arrayList.add(stack.pop());
                    }
                    stack.push(op);
                    i++;
                }
            }
            while (!stack.isEmpty()) {
                arrayList.add(stack.pop());
            }
            return arrayList;
        }
    }
}