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 

        

Answer 1

Using A Simple Regex

One of this method's benefits is that we can easily add tokens besides * (see Adding Tokens at the bottom).

Search: [^*]+|(\*)

• The left side of the | matches any chars that are not a star
• The right side captures all stars to Group 1
• If Group 1 is empty: replace with \Q + Match + E
• If Group 1 is set: replace with .*

Here is some working code (see the output of the online demo).

Input: audio*2012*.wav

Output: \Qaudio\E.*\Q2012\E.*\Q.wav\E

String subject = "audio*2012*.wav";
Pattern regex = Pattern.compile("[^*]+|(\\*)");
Matcher m = regex.matcher(subject);
StringBuffer b= new StringBuffer();
while (m.find()) {
    if(m.group(1) != null) m.appendReplacement(b, ".*");
    else m.appendReplacement(b, "\\\\Q" + m.group(0) + "\\\\E");
}
m.appendTail(b);
String replaced = b.toString();
System.out.println(replaced);

Adding Tokens

Suppose we also want to convert the wildcard ?, which stands for a single character, by a dot. We just add a capture group to the regex, and exclude it from the matchall on the left:

Search: [^*?]+|(\*)|(\?)

In the replace function we the add something like:

else if(m.group(2) != null) m.appendReplacement(b, ".");