개발이 하고 싶어요

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;	

class Solution {
		public static String rangeExtraction(int[] arr) {
    		int length = arr.length;
        Arrays.sort(arr);
        int idx = 0, idx2 = 0;
        List<String> result = new ArrayList<String>();
        while (idx < length) {
            while (++idx2 < length && arr[idx2] - arr[idx2 - 1] == 1);
            if (idx2 - idx > 2) {
            	result.add(new String(arr[idx]+"-"+arr[idx2 - 1]));
                idx = idx2;
            } else {
                for (; idx < idx2; idx++)
                	result.add(new String(arr[idx]+""));
            }
        }
		
        
        return result.stream().collect(Collectors.joining(","));
    }
}