十进制 220 转换为二进制后为？

package 栈的利用;

import java.util.Scanner;

import java.util.Stack;

/***

 * 数值转换

 * 要求：将十进制数转换成指定进制数

 * 解决：利用栈的思想将每次除余得值存在栈中，最后出栈输出

 * 

 * */

public class 数值转换 {

private static Scanner in;

public static void main(String[] args) {

in = new Scanner(System.in);

while (true) {

System.out.println("输入十进制：");

String num = in.next();

System.out.println("转换到n进制：");

int n = in.nextInt();

String result = numTransform(num,n);

System.out.println(result);

}

}

private static String numTransform(String str, int n) {

//int a = Integer.valueOf("23").intValue();

int num = Integer.parseInt(str);

Stack<Integer> stack = new Stack<Integer>(); 

while(true){

stack.push((int)num%n);

if((int)(num/n)==0){

break;

}else{

num /= n;

}

}

StringBuffer res = new StringBuffer();

while(!stack.isEmpty()){

res.append(stack.pop());

}

return res.toString();

}

}