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Tip of the Day
Language: Java
Expertise: Advanced
Dec 13, 2004



Building the Right Environment to Support AI, Machine Learning and Deep Learning

Use a Filter to Retrieve a Specific Subset of Files in a Directory

In Java, File.list() lists all the files in a directory. However, rather than listing all the files and then discarding unnecessary files in your code, this tip will show you how to use a filter to retrieve a specific subset of files.

java.io.FilenameFilter is an interface which can be used to get only that set of files that match a specific criteria. Implement this interface to provide your logic of filtering:

public class FileExtensionFilter implements FilenameFilter{
   private String ext="*";
   public FileExtensionFilter(String ext){
     this.ext = ext;
   public boolean accept(File dir, String name){
     if (name.endsWith(ext))
       return true;
     return false;
To use this filter in your code:

File f = new File("C:\\sample");
FileExtensionFilter filter = new FileExtensionFilter(".java");
String[] contents = f.list(filter);
This example returns only those files with a .java extension.
Amit Tuli
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