public class Solution {

public String reverseVowels(String s) {

if (s == null)

return null;

char[] chars = s.toCharArray();

int left = 0;

int right = s.length() - 1;

while (left < right) {

while (left < right && !isVowel(chars[left]))

left++;

while (left < right && !isVowel(chars[right]))

right--;

char tmp = chars[left];

chars[left] = chars[right];

chars[right] = tmp;

left++;

right--;

}

return String.valueOf(chars);

}

private boolean isVowel(char c) {

switch (c) {

case 'a': // fall through

case 'A': // fall through

case 'e': // fall through

case 'E': // fall through

case 'i': // fall through

case 'I': // fall through

case 'o': // fall through

case 'O': // fall through

case 'u': // fall through

case 'U':

return true;

default:

return false;

}

}

}