多进制计算器 java

基本思路，先将其余进制转化为10进制，然后只需要写出来十进制的计算器就可以了。
总体代码如下：

package bishi.shunfeng;

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

public class jsq {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.nextLine();
        int n = scanner.nextInt();
        String ss = Decimal_conversion(s,n);
        System.out.println(calculate(ss,0)[0]);
    }
    /*
    将n进制转化为10进制
     */
    private static String Decimal_conversion(String s , int n){
      int start = 0;
      StringBuilder res = new StringBuilder();
      while (!Character.isDigit(s.charAt(start))) {
          res.append(s.charAt(start));
          start++;
      }
      String temp = "";
        for (int i = start; i < s.length(); i++) {
            if(!Character.isDigit(s.charAt(i))){
                if(!"".equals(temp))
                {
                    res.append(""+Integer.parseInt(temp,n));
                }
                res.append(s.charAt(i));
                temp = "";
            }
            if(Character.isDigit(s.charAt(i)))
            {
                temp += s.charAt(i);
            }
            if(i == s.length() - 1){
                if(!"".equals(temp))
                {
                    res.append(""+Integer.parseInt(temp,n));
                }
            }
        }

      return res.toString();
    }

    // 十进制计算器
    public int calculate(String s) {
      return calculate(s,0)[0];
    }
    private static int[] calculate(String s ,int index){
        Stack<Integer> stack = new Stack<>();
        int[] res = new int[2];
        int num = 0;
        char flag = '+';
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if(c =='(') {
                int[] temp = calculate(s.substring(i + 1) ,i + 1);
                num = temp[0];
                if(temp[1] == s.length())
                    temp[1] = s.length() - 1;
                c = s.charAt(temp[1]);
                i = temp[1];
            }
            if(Character.isDigit(c)){
               num = num * 10 +  (c - '0' );
            }
            if(!Character.isDigit(c) && c != ' ' || c == ')' || i >= s.length() - 1){
                switch (flag){
                    case '-':{

                        stack.push(-num); num = 0; flag = c ;break;
                    }
                    case '+': stack.push(num);num = 0; flag = c;break;
                    case '*':stack.push(stack.pop() * num); num = 0;flag = c; break;
                    case '/':stack.push((int) (stack.pop() / (float)num));num = 0 ; flag = c ; break;
                }
            }

            if(c == ')') {
                res[1] = i + 1 + index;
                break;
            }
        }

        res[0] = sum_stack(stack);
        return res;
    }
    //对栈求值
    private static int sum_stack(Stack<Integer> stack) {
        int res = 0;
        while (!stack.isEmpty()){
            res += stack.pop();
        }
        return  res;
    }
}