Java.Streams.What do you know about the FileFilter interface?

📘 What is FileFilter?

• It’s part of java.io.
• It’s a functional interface with one method:

boolean accept(File pathname);

Used to filter files or directories based on your logic (e.g., extension, size, name pattern).

🔧 Common Use Case

Used with:

File[] filteredFiles = directory.listFiles(FileFilter filter);

✅ Example: Filter .txt Files

import java.io.*;

public class TxtFileFilterDemo {
    public static void main(String[] args) {
        File dir = new File("documents");

        File[] txtFiles = dir.listFiles(new FileFilter() {
            @Override
            public boolean accept(File file) {
                return file.getName().endsWith(".txt");
            }
        });

        for (File file : txtFiles) {
            System.out.println(file.getName());
        }
    }
}

🧠 Java 8+ Lambda Version

Because it’s a functional interface, you can use a lambda:

File[] txtFiles = dir.listFiles(file -> file.getName().endsWith(".txt"));

Much cleaner! 🧼

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💡 Real-World Uses

Scenario	Filter Logic
Only images	`name.endsWith(“.jpg”)
Only directories	file.isDirectory()
Files > 1MB	file.length() > 1024 * 1024

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🧵 TL;DR

Feature	Description
Type	@FunctionalInterface
Method	boolean accept(File pathname)
Purpose	Filter files returned by listFiles()
Added in	Java 1.2
Alternative	FilenameFilter (older, takes name as string)