Question

I started writing this algorithm:

public static String convert(String str) {
    if (str.equals("# "))
        return " ";

    if (str.matches("#+.+")) {
        int n = str.length() - str.replaceFirst("#+", "").length();
        return "<h" + n + ">" + str.substring(n) + "<h" + n + ">";
    }

    return str;
}
}

So when I type, ####title, it returns < h4>title< /h4>

My problem is that when I write ####title###title, I would like it to return < h4>title< /h4> < h3>title< /h3> but it only returns < h4>title< /h4>…What am I doing wrong???

Answer 1

Thats because you are using the pattern: – #+.+.

Now, since . matches everything in Regex, so in the above pattern, it matches everything after an initial set of #'s.

So, for your input: – ####title###title, your pattern will match: –

• #+ will match ####
• .+ will match title###title

You need to change your regex to : – (#+[^#]+), and probably need to use Pattern class here to get the desired output, becaues you want to match every part of your string to the given pattern.

#+[^#]+ -> Will match the first set of # and then everything after that, except #. So it stops where the next set of #'s start.

Here’s how you can use it: –

    String str = "####title###title";  // str is the method parameter
    if (str.equals("# "))
        System.out.println(" ");

    Pattern pattern = Pattern.compile("(#+[^#]+)");
    Matcher matcher = pattern.matcher(str);

    while (matcher.find()) {
        String str1 = matcher.group(1);
        int n = str1.length() - str1.replaceFirst("#+", "").length();
        System.out.println("<h" + n + ">" + str1.substring(n) + "</h" + n + ">");
    }

OUTPUT: –

<h4>title</h4>
<h3>title</h3>