Reverse Vowels of a String

Write a function that takes a string as input and reverse only the vowels of a string.

Example 1:
Given s = "hello", return "holle".

Example 2:
Given s = "leetcode", return "leotcede".

Note:
The vowels does not include the letter "y".

vowels:元音aeiou

解法：two pointers

public class Solution {
public String reverseVowels(String s) {
String vowel = "aeiouAEIOU";
int start = 0;
int end = s.length()-1;
char[] chars = s.toCharArray();
while(start<end)
{
while(start<end&&!vowel.contains(chars[start]+""))
{
start++;
}
while(start<end&&!vowel.contains(chars[end]+""))
{
end--;
}

char temp = chars[start];
chars[start]=chars[end];
chars[end]=temp;
start++;
end--;
}

return String.valueOf(chars);

}
}

chars[end]+"" 这里加上“”很重要，不然会出以下错误：

error: incompatible types: char cannot be converted to CharSequence