Question

I need to implement

File[] files = getFiles( String folderName, String ptrn );

Where ptrn is a command prompt style pattern like “*2010*.txt”

I’m familar with FilenameFilter class, but can’t implement
public boolean accept(File dir, String filename)
because String.matches() doesn’t accept such patterns.

Thanks!

Answer 1

The String#matches() accepts regular expression patterns.

The regex variant of the “layman’s” variant *2010*.txt would be .*2010.*\.txt.

So the following should work:

public boolean accept(File dir, String name) {
    return name.matches(".*2010.*\\.txt");
}

The double backslash is just there to represent an actual backslash because the backslash itself is an escape character in Java’s String.

Alternatively, you can also do it without regex using the other String methods:

public boolean accept(File dir, String name) {
    return name.contains("2010") && name.endsWith(".txt");
}

Your best bet is likely to let ptrn represent a real regex pattern or to string-replace every . with \. and * with .* so that it becomes a valid regex pattern.

public boolean accept(File dir, String name) {
    return name.matches(ptrn.replace(".", "\\.").replace("*", ".*"));
}