504. Base 7

Given an integer, return its base 7 string rePResentation.

Example 1:

Input: 100Output: "202"
Example 2:
Input: -7Output: "-10"
Note: The input will be in range of [-1e7, 1e7].
public class demo1 {		public String convertToBase7(int num) {					String result="";				if(num==0) result="0";		int number=Math.abs(num);		while (number>0) {			int b=number%7;			number=number/7;			result=String.valueOf(b)+result;		}				if(num<0) {			result="-"+result;					}		return result;			}				public static void main(String[] args){    	int num=-7;    	demo1 r = new demo1();         	System.out.println(r.convertToBase7(num));	}}提交答案后，看到leetcode讨论区中的一个答案，只有五行，递归，简单到爆，特地copy过来膜拜膜拜。
public String convertToBase7(int num) {		 if (num < 0)		        return '-' + convertToBase7(-num);		    if (num < 7)		        return num + "";		    return convertToBase7(num / 7) + num % 7;		  	    	}