如何将字符串中第一次出现的字符大写

Question

我有一个字符串“aabccdeef”

现在我只想大写每个字符的第一次出现，以便在Java中o/p是AaBCcDEeF

Answer 1

 public static String capitalizeFirstOccurrence(String str) {
    var alreadyOccurred = new HashSet<String>();
    return str.chars()
            .mapToObj(x -> String.valueOf((char) x)) // convert to single char String
            .map(character -> {
                if (alreadyOccurred.contains(character)) {
                    return character;
                }
                alreadyOccurred.add(character);
                return character.toUpperCase();
            })
            .collect(Collectors.joining());
}

public static void main(String[] args) {
    var input = "aabccdeef";
    var output = capitalizeFirstOccurrence(input);
    System.out.println(output);
}