Using FileFilter in Java

What need to do when you want to filter files by extensions in directory?

There are 2 ways:

implement FileFilter or FilenameFilter.

I am going to show how to do this with FileFilter.

FileFilter is an interface for filtering File objects based on their names or other information.

Example:

class ProjectFilter implements FileFilter{ private String[] extension ={"java","xml"}; @Override  public boolean accept(File pathname){ if (pathname.isDirectory()){ return true; }  String name = pathname.getName().toLowerCase(); for (String anExt:extension){ if (name.endsWith(anExt)){return true; }  }  return false; }}

Now just use ProjectFilter object in listFiles method.

Example:

File dir = new File("C:/sample_dir");File[] files = dir.listFiles(new ProjectFilter())

In this case in array files will presents files with extensions java and xml.

Full example:

import java.io.File;import java.io.FileFilter;public class Main{ public static void main(String[] args){ File dir = new File("D:/project/sample_dir"); File[] files = dir.listFiles(new ProjectFilter()); for (File f:files){ System.out.println(f.getAbsolutePath()); }  }  private static class ProjectFilter implements FileFilter{ private String[] extension ={"java","xml"}; @Override  public boolean accept(File pathname){ if (pathname.isDirectory()){return true; }  String name = pathname.getName().toLowerCase(); for (String anExt:extension){if (name.endsWith(anExt)){return true;}  }  return false; }  }}

File filtering is very simple operation in Java.

For this post I used JDK 6.