Wildcard matching in Java

Question

I'm writing a simple debugging program that takes as input simple strings that can contain stars to indicate a wildcard match-any

*.wav  // matches <anything>.wav
(*, a) // matches (<anything>, a)

I thought I would simply take that pattern, escape any regular expression special characters in it, then replace any \\* back to .*. And then use a regular expression matcher.

But I can't find any Java function to escape a regular expression. The best match I could find is Pattern.quote, which however just puts \Q and \E at the begin and end of the string.

Is there anything in Java that allows you to simply do that wildcard matching without you having to implement the algorithm from scratch?

Answer 1

Just escape everything - no harm will come of it.

    String input = "*.wav";
    String regex = ("\\Q" + input + "\\E").replace("*", "\\E.*\\Q");
    System.out.println(regex); // \Q\E.*\Q.wav\E
    System.out.println("abcd.wav".matches(regex)); // true

Or you can use character classes:

    String input = "*.wav";
    String regex = input.replaceAll(".", "[$0]").replace("[*]", ".*");
    System.out.println(regex); // .*[.][w][a][v]
    System.out.println("abcd.wav".matches(regex)); // true

It's easier to "escape" the characters by putting them in a character class, as almost all characters lose any special meaning when in a character class. Unless you're expecting weird file names, this will work.