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To retrieve all files in a folder in Java, you can use the File class provided in the standard library. Here's how you can do it:

✅ Step-by-Step Example:

java

import java.io.File;

public class FileLister {

    public File[] getAllFilesInFolder(String folderPath) {
        File folder = new File(folderPath);
        if (folder.isDirectory()) {
            return folder.listFiles(); // All files and subdirectories
        } else {
            System.out.println("The provided path is not a directory.");
            return new File[0];
        }
    }

    public static void main(String[] args) {
        FileLister fileLister = new FileLister();
        String folderPath = "your/folder/path/here"; // Replace with actual path
        File[] files = fileLister.getAllFilesInFolder(folderPath);

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

💡 Notes:

• listFiles() returns both files and subdirectories.
• To only get files, you can use:

java

File[] filesOnly = folder.listFiles(File::isFile);

• To filter files by extension:

java

File[] textFiles = folder.listFiles((dir, name) -> name.endsWith(".txt"));

📁 Title:

How to List Only Folders in a Directory Using Java

🔑 Keywords:

Java Directory Listing, Java Folders Only, List Directories Java, File API Java, Java Folder Filter, Java File System, Directory Traversal

📝 Article:

You can list only the folders (i.e., directories) in a specified path using the File class and a built-in directory filter:

✅ Sample Code:

java

import java.io.File;

public class DirectoryLister {

    public File[] getAllFoldersInDirectory(String directoryPath) {
        File directory = new File(directoryPath);
        if (directory.isDirectory()) {
            return directory.listFiles(File::isDirectory); // Only folders
        } else {
            System.out.println("The provided path is not a directory.");
            return new File[0];
        }
    }

    public static void main(String[] args) {
        DirectoryLister lister = new DirectoryLister();
        String path = "your/directory/path/here";
        File[] folders = lister.getAllFoldersInDirectory(path);

        for (File folder : folders) {
            System.out.println(folder.getName());
        }
    }
}

💡 Notes:

• This method does not recurse into nested folders.
• You can apply custom filters or sorting as needed.

📁 Title:

Map Subdirectories to Their Files in Java

🔑 Keywords:

Java File Mapping, Java Directory Structure, Map Folders to Files Java, Subdirectory Files Java, Java File Explorer, Java IO Mapping

📝 Article:

To map each subdirectory to its list of files in Java (using a Map<String, File[]>), follow this approach:

✅ Full Example:

java

import java.io.File;
import java.util.HashMap;
import java.util.Map;

public class DirectoryFileMapper {

    public Map<String, File[]> getDirectoryFiles(String folderPath) {
        Map<String, File[]> directoryFiles = new HashMap<>();
        File folder = new File(folderPath);

        if (folder.isDirectory()) {
            File[] subdirectories = folder.listFiles(File::isDirectory);

            if (subdirectories != null) {
                for (File subdirectory : subdirectories) {
                    File[] files = subdirectory.listFiles(File::isFile);
                    directoryFiles.put(subdirectory.getName(), files);
                }
            }
        } else {
            System.out.println("The provided path is not a directory.");
        }

        return directoryFiles;
    }

    public static void main(String[] args) {
        DirectoryFileMapper mapper = new DirectoryFileMapper();
        String path = "your/folder/path/here";
        Map<String, File[]> map = mapper.getDirectoryFiles(path);

        for (Map.Entry<String, File[]> entry : map.entrySet()) {
            System.out.println("Directory: " + entry.getKey());
            for (File file : entry.getValue()) {
                System.out.println("  File: " + file.getName());
            }
        }
    }
}

💡 Notes:

• This maps only direct subdirectories and their immediate files.
• If needed, you can write a recursive version to go deeper.