Question

Overview

I’m in the process of porting a simple utility app over from C# into Java and as part of this I’m writing some helper methods for items where I prefer C#’s semantics. Once such case is Directory.GetFiles.

Current Code

import java.io.File;
import java.io.FilenameFilter;

public class Directory {
    public static String[] GetFiles(String path) {        
        File directory = new File(path);
    
         return directory.list(new FilenameFilter() {
            @Override
            public boolean accept(File dir, String filename) {
                return new File(dir, filename).isFile();
            }
        });
     }
}

Question

Whilst the above all seems fine, and replicates one of the GetFiles overloads, I’m stuck on how best to write a method that replicates the functionality of C#’s Directory.GetFiles(String, String).

This method should take a path string, as well as a searchPattern, which is used to return only files matching that particular pattern.

For example, each of the following should work:

// Used to get all JavaScript files
Directory.GetFiles("~/Documents/", "*.js");

// Get all CSS files in the styles sub-folder.
Directory.GetFiles("~/Documents/", "styles/*.css"); 

Answer 1

You could modify the pattern by placing a period before each asterisk and question mark, and then use this as a regular expression to determine which files you should return. So, you could write something like

public static String[] GetFiles(final String path, final String searchPattern) {
    final Pattern re = Pattern.compile(searchPattern.replace("*", ".*").replace("?", ".?"));
    return new File(path).list(new FilenameFilter() {
        @Override
        public boolean accept(File dir, String name) {
            return new File(dir, name).isFile() && re.matcher(name).matches();
        }
    });
}