面试题：把数组排成最小的数

import java.util.ArrayList;
import java.util.Comparator;
import java.util.Arrays;
public class Solution {
    public String PrintMinNumber(int [] numbers) {
        if(numbers==null||numbers.length==0) return "";
        int len=numbers.length;
        String[] str=new String[len];
        StringBuffer sb=new StringBuffer();
        for(int i=0;i<len;i++){
            str[i]=String.valueOf(numbers[i]);
        }
        //重写Comparator函数
        Arrays.sort(str,new Comparator<String>(){
            public int compare(String s1,String s2){
                String c1=s1+s2;
                String c2=s2+s1;
                return c1.compareTo(c2);
            }
        });
        for(int i=0;i<len;i++){
            sb.append(str[i]);
        }
        return sb.toString();
    }
}