Arrange Largest Number into String

ArrangeLargestNumber.java

public class Solution {
    public String largestNumber(int[] num) {
        
         String[] arr = new String[num.length];
        
         for (int i = 0; i < num.length; i++){
             arr[i] = Integer.toString(num[i]);
         }
         
         Comparator<String> comp = new Comparator<String>(){
            @Override
            public int compare(String str1, String str2){
                String s1 = str1+str2;
                String s2 = str2+str1;
                return s2.compareTo(s1);
            }
        };
        
        Arrays.sort(arr, comp);
       
        if (arr[0].charAt(0) == '0') return "0";
        
        StringBuffer buff= new StringBuffer();
        for (int i = 0; i < arr.length; i++){
            buff.append(arr[i]);
        }
        
        return buff.toString();
    }
}