How do I use regex to match split characters in java?

Question

For this code, all I want to do is split the original string into words by spaces and use regex to return the words that are not y, 4, !, or ?

However, I'm not sure why this isn't working:

    public static void main (String[] args) {
    System.out.println(makeWords("y are you not 4 !?"));
    //should return string "are you not"
}

public static String makeWords (String str) {
    String[] word = str.split(" ");
    //make array of words
    String result = "";
    for (int i = 0; i < word.length; i++) {
        if (word[i].matches("[^y4!?]")) {
            String str = word[i];
            result += str;
        }
    }
    return result;
}

}

Answer 1

Your regex checks for words that are a single character (and that character must not match 'y', '4', '!', or '?'). None of your words meet that specification, so your result is empty string.

I think you need to change it like this:

public static String makeWords(String str) {
    String[] word = str.split(" ");
    // make array of words
    String result = "";
    for (int i = 0; i < word.length; i++) {
        if (!word[i].matches("[y4!?]+")) {
            String s = word[i];
            result += s + " ";
        }
    }
    return result;
}

This returns words that are one or more characters ( + ) and not consisting of combinations of y4!? .

System.out.println(makeWords("y are you not 4 !?"));

Produces:

are you not