FileTreeExample.java

import javax.swing.*;
import javax.swing.tree.DefaultMutableTreeNode;
import java.io.File;

public class FileTreeExample {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            JFrame frame = new JFrame("Root Directory and Subfolders");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setSize(500, 500);

            // Get the system root directories
            File[] roots = File.listRoots();

            // Create the root node for JTree
            DefaultMutableTreeNode rootNode = new DefaultMutableTreeNode("Root Directories");

            for (File root : roots) {
                DefaultMutableTreeNode rootDirNode = new DefaultMutableTreeNode(root.getPath());
                rootNode.add(rootDirNode);

                // Add subdirectories of the root directory
                addSubFolders(root, rootDirNode);
            }

            // Create JTree with the root node
            JTree tree = new JTree(rootNode);
            JScrollPane scrollPane = new JScrollPane(tree);

            frame.add(scrollPane);
            frame.setVisible(true);
        });
    }

    private static void addSubFolders(File folder, DefaultMutableTreeNode node) {
        File[] subFolders = folder.listFiles(File::isDirectory);
        if (subFolders != null) {
            for (File subFolder : subFolders) {
                DefaultMutableTreeNode subNode = new DefaultMutableTreeNode(subFolder.getName());
                node.add(subNode);

                // Recursively add subfolders of this folder
                addSubFolders(subFolder, subNode);
            }
        }
    }
}