How do I create JTree with different icons for each node?

The example below demonstrates you how to create a JTree that have a different icons for each node of the tree.

package org.kodejava.example.swing;

import javax.swing.*;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreeCellRenderer;
import java.awt.*;
import java.net.URL;

public class JTreeDifferentNodeIcon extends JFrame {
    public JTreeDifferentNodeIcon() throws HeadlessException {
        initializeUI();
    }

    private void initializeUI() {
        setSize(200, 400);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        DefaultMutableTreeNode root = new DefaultMutableTreeNode("Countries");
        DefaultMutableTreeNode asia = new DefaultMutableTreeNode("Asia");
        Country[] countries = new Country[]{
                new Country("India", "/flags/in.png"),
                new Country("Singapore", "/flags/sg.png"),
                new Country("Indonesia", "/flags/id.png"),
                new Country("Vietnam", "/flags/vn.png"),
        };

        for (Country country : countries) {
            DefaultMutableTreeNode node = new DefaultMutableTreeNode(country);
            asia.add(node);
        }

        DefaultMutableTreeNode northAmerica = new DefaultMutableTreeNode("North America");
        countries = new Country[]{
                new Country("United States", "/flags/us.png"),
                new Country("Canada", "/flags/ca.png")
        };

        for (Country country : countries) {
            DefaultMutableTreeNode node = new DefaultMutableTreeNode(country);
            northAmerica.add(node);
        }

        DefaultMutableTreeNode southAmerica = new DefaultMutableTreeNode("South America");
        countries = new Country[]{
                new Country("Brazil", "/flags/br.png"),
                new Country("Argentina", "/flags/ar.png"),
                new Country("Uruguay", "/flags/uy.png")
        };
        for (Country country : countries) {
            DefaultMutableTreeNode node = new DefaultMutableTreeNode(country);
            southAmerica.add(node);
        }

        DefaultMutableTreeNode europe = new DefaultMutableTreeNode("Europe");
        countries = new Country[]{
                new Country("United Kingdom", "/flags/gb.png"),
                new Country("Germany", "/flags/de.png"),
                new Country("Spain", "/flags/es.png"),
                new Country("France", "/flags/fr.png"),
                new Country("Italy", "/flags/it.png")
        };
        for (Country country : countries) {
            DefaultMutableTreeNode node = new DefaultMutableTreeNode(country);
            europe.add(node);
        }

        root.add(asia);
        root.add(northAmerica);
        root.add(southAmerica);
        root.add(europe);

        final JTree tree = new JTree(root);
        tree.setCellRenderer(new CountryTreeCellRenderer());

        JScrollPane pane = new JScrollPane(tree);
        pane.setPreferredSize(new Dimension(200, 400));

        getContentPane().setLayout(new BorderLayout());
        getContentPane().add(pane, BorderLayout.CENTER);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new JTreeDifferentNodeIcon().setVisible(true);
            }
        });
    }

    class CountryTreeCellRenderer implements TreeCellRenderer {
        private JLabel label;

        CountryTreeCellRenderer() {
            label = new JLabel();
        }

        public Component getTreeCellRendererComponent(JTree tree, Object value, boolean selected, boolean expanded,
                                                      boolean leaf, int row, boolean hasFocus) {
            Object o = ((DefaultMutableTreeNode) value).getUserObject();
            if (o instanceof Country) {
                Country country = (Country) o;
                URL imageUrl = getClass().getResource(country.getFlagIcon());
                if (imageUrl != null) {
                    label.setIcon(new ImageIcon(imageUrl));
                }
                label.setText(country.getName());
            } else {
                label.setIcon(null);
                label.setText("" + value);
            }
            return label;
        }
    }

    class Country {
        private String name;
        private String flagIcon;

        Country(String name, String flagIcon) {
            this.name = name;
            this.flagIcon = flagIcon;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public String getFlagIcon() {
            return flagIcon;
        }

        public void setFlagIcon(String flagIcon) {
            this.flagIcon = flagIcon;
        }
    }
}

Here is the result of our program above:

JTree with different icon for each node

Flag icons provided by FamFamFam Flag Icons.

How do I get the selected nodes of a JTree?

The following example show how to use the JTree.getSelectionPaths() method to get the selected node of a JTree component. This method returns an array of TreePath objects. In the case to get the last node in the path we can call the TreePath.getLastPathComponent().

In the code below when you pressed the button the listener gets the selection paths and print out the last path component of the selected nodes.

package org.kodejava.example.swing;

import javax.swing.*;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreePath;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class JTreeGetSelectedNode extends JFrame {
    public JTreeGetSelectedNode() throws HeadlessException {
        initializeUI();
    }

    private void initializeUI() {
        setSize(200, 400);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        DefaultMutableTreeNode root = new DefaultMutableTreeNode("Countries");
        DefaultMutableTreeNode asia = new DefaultMutableTreeNode("Asia");
        String[] countries = new String[] {"India", "Singapore", "Indonesia", "Vietnam"};
        for (String country : countries) {
            DefaultMutableTreeNode node = new DefaultMutableTreeNode(country);
            asia.add(node);
        }

        DefaultMutableTreeNode northAmerica = new DefaultMutableTreeNode("North America");
        countries = new String[] {"United States", "Canada"};
        for (String country : countries) {
            DefaultMutableTreeNode node = new DefaultMutableTreeNode(country);
            northAmerica.add(node);
        }

        DefaultMutableTreeNode southAmerica = new DefaultMutableTreeNode("South America");
        countries = new String[] {"Brazil", "Argetina", "Uruguay"};
        for (String country : countries) {
            DefaultMutableTreeNode node = new DefaultMutableTreeNode(country);
            southAmerica.add(node);
        }

        DefaultMutableTreeNode europe = new DefaultMutableTreeNode("Europe");
        countries = new String[] {"United Kingdom", "Germany", "Spain", "France", "Italy"};
        for (String country : countries) {
            DefaultMutableTreeNode node = new DefaultMutableTreeNode(country);
            europe.add(node);
        }

        root.add(asia);
        root.add(northAmerica);
        root.add(southAmerica);
        root.add(europe);

        final JTree tree = new JTree(root);
        JScrollPane pane = new JScrollPane(tree);
        pane.setPreferredSize(new Dimension(200, 400));


        JButton button = new JButton("Get Selected");
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                TreePath[] paths = tree.getSelectionPaths();

                for (TreePath path : paths) {
                    System.out.println("You've selected: " + path.getLastPathComponent());
                }
            }
        });

        getContentPane().setLayout(new BorderLayout());
        getContentPane().add(pane, BorderLayout.CENTER);
        getContentPane().add(button, BorderLayout.SOUTH);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new JTreeGetSelectedNode().setVisible(true);
            }
        });
    }
}