剑指offer-把数组排成最小的数

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;

public class Solution {
    public String PrintMinNumber(int [] numbers) {
        if(numbers ==null ||numbers.length<=0){
            return new String();
        }
        Integer[] nums = new Integer[numbers.length];
        for(int i=0;i<numbers.length;i++){
            nums[i] = numbers[i];
        }
        Arrays.sort(nums,new Comparator<Integer>(){
            public int compare(Integer o1,Integer o2){
                int val1 = Integer.valueOf(String.valueOf(o1)+String.valueOf(o2));
                int val2 = Integer.valueOf(String.valueOf(o2)+String.valueOf(o1));
                return val1-val2;
            }
        });
        StringBuilder re =new StringBuilder();
        for(int i =0;i<nums.length;i++){
            re.append(nums[i]);
        }
        return re.toString();
    }
}