feat: java code for leetcode-345

Author: KGK-7

Reverse vowels of a string.java

@@ -0,0 +1,21 @@
+class Solution {
+    public String reverseVowels(String s) {
+        HashSet<Character> vowels = 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){
+            while(left < right && !vowels.contains(arr[left])) left++;
+            while(left < right && !vowels.contains(arr[right])) right--;
+
+            char temp = arr[left];
+            arr[left] = arr[right];
+            arr[right] = temp;
+
+            left++ ;
+            right-- ;
+        }
+        return new String(arr);
+    }
+
+}