把数组排成最小的数

题目描述
输入一个正整数数组，把数组里所有数字拼接起来排成一个数，打印能拼接出的所有数字中最小的一个。例如输入数组{3，32，321}，则打印出这三个数字能排成的最小数字为321323。
python思路：转换成字符串+比较大小，交换字符串位置，然后遍历输出字符串

# -*- coding:utf-8 -*-
class Solution:
    def PrintMinNumber(self, numbers):
        # write code here
        if not numbers:
            return ""
        num=map(str,numbers) #先转成字符串
        for i in range(len(numbers)):
            for j in range(i+1,len(numbers)):
                if(int(num[i]+num[j]))>int(num[j]+num[i]):
                    num[i],num[j]=num[j],num[i]
        res=''
        for i in range(len(numbers)):
            res+=num[i]
        return res

1.先将数组加入arraylist
2.对arraylist自定义排序
？JAVA collection,sort()重写Compare

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

public class Solution {
    public String PrintMinNumber(int [] numbers) {
        ArrayList<Integer> list = new ArrayList<>();
        String res = "";
 
        if (numbers.length == 0) return "";
        if (numbers.length == 1) return String.valueOf(numbers[0]);//整数转成string格式
        for (int i = 0; i < numbers.length; i++)
            list.add(numbers[i]);
        Collections.sort(list, new Comparator<Integer>() {
            public int compare(Integer o1, Integer o2) {//重写compare，升序排序
                String s1 = o1 + "" + o2;
                String s2 = o2 + "" + o1;
                return s1.compareTo(s2);
            }
        });
        for (Integer l : list)
            res = res + l;//与字符串相加得到字符串形式
        return res;
    }
}