Question

I am compiling a regex patter to match specific commands in a debug console, one of them is:

Pattern.compile("^\\s*\\\\connect\\s+((\\d{1,3}\\.){3}\\d{1,3})(?:\\s+(\\d+))?\\s*$");

so it is possible to enter

\connect 127.0.0.1 2345

or leave the port

\connect 127.0.0.1

spaces are ignored as long as I use at last one space to separate the fields.

It works perfectly, however, while the ip goes to group 1 (which is ok), the port goes to group 3 (as written, I know).

So I wanted to use an non-capturing group for the first three parts of the ip address:

Pattern.compile("^\\s*\\\\connect\\s+((?:\\d{1,3}\\.){3}\\d{1,3})(?:\\s+(\\d+))?\\s*$");

So I thought I would get the ip in group 1 and the port in group 2.
But now the Matcher.matches() returns false for the same input… Where is the problem?

Answer 1

Wild guess: The problem is somewhere else.
I did a quick test:

        String test = "\\connect 127.0.0.1 2345";
    Pattern p1 = Pattern.compile("^\\s*\\\\connect\\s+((\\d{1,3}\\.){3}\\d{1,3})(?:\\s+(\\d+))?\\s*$");
    Pattern p2 = Pattern.compile("^\\s*\\\\connect\\s+((?:\\d{1,3}\\.){3}\\d{1,3})(?:\\s+(\\d+))?\\s*$");

    System.out.println(p1.matcher(test).matches());
    System.out.println(p2.matcher(test).matches());

Output:
true
true