HDOJ 1335 Basically Speaking(进制转换)

Problem Description
The Really Neato Calculator Company, Inc. has recently hired your team to help design their Super Neato Model I calculator. As a computer scientist you suggested to the company that it would be neato if this new calculator could convert among number bases. The company thought this was a stupendous idea and has asked your team to come up with the prototype program for doing base conversion. The project manager of the Super Neato Model I calculator has informed you that the calculator will have the following neato features:
It will have a 7-digit display.

Its buttons will include the capital letters A through F in addition to the digits 0 through 9.

It will support bases 2 through 16.

Input
The input for your prototype program will consist of one base conversion per line. There will be three numbers per line. The first number will be the number in the base you are converting from. The second number is the base you are converting from. The third number is the base you are converting to. There will be one or more blanks surrounding (on either side of) the numbers. There are several lines of input and your program should continue to read until the end of file is reached.

Output
The output will only be the converted number as it would appear on the display of the calculator. The number should be right justified in the 7-digit display. If the number is to large to appear on the display, then print “ERROR” (without the quotes) right justified in the display.

Sample Input

1111000  2 10
1111000  2 16
2102101  3 10
2102101  3 15
  12312  4  2
     1A 15  2
1234567 10 16
   ABCD 16 15

Sample Output

    120
     78
   1765
    7CA
  ERROR
  11001
 12D687
   D071

输入3个数：n a b
输入的n是a进制的数，需要把n再转换成b进制的数。
如果转换之后的数字位数超过了7，就输出“ ERROR”。
每个输出占7位，不足7位的左边补空格。

import java.util.Scanner;

public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            String strNum = sc.next();
            int a = sc.nextInt();
            int b = sc.nextInt();

            int s = Integer.valueOf(strNum, a);
            //将a进制的strNum转换成10进制s
            String sNum = Integer.toString(s, b);

            if(sNum.length()>7){
                System.out.println(" ERROR");
                continue;
            }

            for(int i=7;i>sNum.length();i--){
                System.out.print(" ");
            }
            System.out.println(sNum.toUpperCase());

        }

    }

}