Counting unique characters in a String given by the user

Question

I have to write a program that counts the uniques characters in a String given by the user. For example \"abc\" returns 3 and \"aabbccd\" returns 4. I am not allow to use advan

Answer 1

Using Java 8 you could do the following:

public static long countUniqueCharacters(String input) {
    return input.chars()
            .distinct()
            .count();
}

This creates an IntStream of chars, then takes only distincts values and then counts the number of occurences.