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

Here another solution:

public static int countUniqueCharacters(String input) {
    String buffer = "";
    for (int i = 0; i < input.length(); i++) {
        if (!buffer.contains(String.valueOf(input.charAt(i)))) {
            buffer += input.charAt(i);
        }
    }
    return buffer.length();
}

The first occurance of each character is stored in buffer. Therefore you have of all characters one in buffer, therefore buffer.length() delivers the count you need.