return new String(array) when you modified array

Precautions

If you modified string to a char array, and you want to return the modified char array, do return new String(array), not just return s. Technically s is not modified - it is the char array that is changed.

This example

public class Solution {
    public String reverseVowels(String s) {
        Set<Character> set = new HashSet<>(Arrays.asList('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'));
        char[] arr = s.toCharArray();
        int left = 0, right = arr.length - 1;
        while (left < right) {
            if (!set.contains(arr[left])) {
                left++;
            } else if (!set.contains(arr[right])) {
                right--;
            } else {
                char tmp = arr[left];
                arr[left] = arr[right];
                arr[right] = tmp;
                left++;
                right--;
            }
        }
        return new String(arr);
    }
}

I tried return s but it does not return the modified string (obviously). You have to return a new String that takes the char array of string.