public int firstUniqChar(String s) {
    HashMap<Character, Integer> charCount = new HashMap<>();

    // Count the occurrences of each character in the string
    for (char val : s.toCharArray()) {
        charCount.put(val, charCount.getOrDefault(val, 0) + 1);
    }

    // Find the index of the first non-repeating character
    for (int i = 0; i < s.length(); i++) {
        if (charCount.get(s.charAt(i)) == 1) {
            return i;
        }
    }

    // If no unique character is found, return -1
    return -1;
}