Question

i wanted to write a file search program where the user can enter the serach pattern(any valid regex) and the file name matching the same will be returned.

e.g MFile123.tx will find UMFile123.txt and AIIMFile123.txs

I tried the following, but it did not work:

import java.util.regex.*;
public class regexTest {
    public static void main(String... a){
        String file="UMFile123.txt";
       //String pattern="*MFile*.tx?"; TRIED with \*MFile*.tx , but no use
        String pattern="UMFile*.tx?";
        Pattern p=Pattern.compile(pattern);
        Matcher m=p.matcher(file);
        if(m.matches()){
            System.out.println("Hi!it matches!!");
        }
    }
}

Answer 1

The simplest solution would be to “quote” or “escape” the user entered file name/pattern and prepend & append a .*? to it. Something like:

final String userFname = "MFile123.tx";
final String escapedName = Pattern.quote(userFname);
final String fnamePattern = ".*?" + escapedName + ".*";
final Pattern pat = Pattern.compile(fnamePattern);
final Matcher m = pat.matcher(file);

I would rather not go with the business of manual escaping as mentioned by the other answers here. Tricky to get right IMHO. If you want case-insensitive match, just throw in one of the insensitive regex flags and you should be good.