我们知道计算机的大小单位有 B, KB, MB 等，现在请你编写一个计算器进行大小单位换算。Java洛谷传智杯

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.next();
        int[] curNum = new int[4];
        int count = 0, Num = 0;
        double toNum = 0;
        char curChar = 0, toChar = 0;
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) == '?'){
                toChar = s.charAt(i + 1);
                break;
            }
        }
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) >= 'A' && s.charAt(i) <= 'Z'){
                curChar = s.charAt(i);
                break;
            }
            curNum[i] = s.charAt(i) - '0';
            count++;
        }
        for (int i = 0; ; i++) {
            Num += curNum[i] * Math.pow(10,count-1);
            count--;
            if (count == 0) break;
        }
        if (curChar == 'G'){
            if (toChar == 'M'){
                toNum = Num * Math.pow(2,10);
            }
            else if (toChar == 'K'){
                toNum = Num * Math.pow(2,20);
            }
            else if (toChar == 'B'){
                toNum = Num * Math.pow(2,30);
            }else toNum = Num;
        }
        if (curChar == 'M'){
            if (toChar == 'G'){
                toNum = Num * Math.pow(2,-10);
            }
            else if (toChar == 'K'){
                toNum = Num * Math.pow(2,10);
            }
            else if (toChar == 'B'){
                toNum = Num * Math.pow(2,20);
            }else toNum = Num;
        }
        if (curChar == 'K'){
            if (toChar == 'G'){
                toNum = Num * Math.pow(2,-20);
            }
            else if (toChar == 'M'){
                toNum = Num * Math.pow(2,-10);
            }
            else if (toChar == 'B'){
                toNum = Num * Math.pow(2,10);
            }else toNum = Num;
        }
        if (curChar == 'B'){
            if (toChar == 'G'){
                toNum = Num * Math.pow(2,-30);
            }else if (toChar == 'M'){
                toNum = Num * Math.pow(2,-20);
            }else if (toChar == 'K'){
                toNum = Num * Math.pow(2,-10);
            }else toNum = Num;
        }
        System.out.printf("%.6f",toNum);
    }
}