剑指offer 把数组排成最小的数

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;

public class Solution {
    public String PrintMinNumber(int [] numbers) {

        String result="";
        ArrayList<Integer> list=new ArrayList<>();
        for (int num:numbers) list.add(num);

        Collections.sort(list, new Comparator<Integer>() {
            @Override
            public int compare(Integer o1, Integer o2) {
                String s1=o1+""+o2;
                String s2=o2+""+o1;
                return s1.compareTo(s2);
            }
        });

        for (int i:list) result+=i;

        return result;
    }
}