How do I change JTree default icons?

By I Wayan Saryada in Swing 0 Comment

The program below demonstrate how to change the default icons of a JTree component. We can change tree icons of the component which are the closed icon, the open icon and the leaf icon.

package org.kodejava.swing;

import javax.swing.*;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeCellRenderer;
import java.awt.*;
import java.util.Objects;

public class JTreeChangeIcon extends JFrame {
    public JTreeChangeIcon() throws HeadlessException {
        intializeUI();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new JTreeChangeIcon().setVisible(true));
    }

    private void intializeUI() {
        setSize(500, 500);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        DefaultMutableTreeNode root = new DefaultMutableTreeNode("Address Book");
        DefaultMutableTreeNode a = new DefaultMutableTreeNode("A");
        DefaultMutableTreeNode b = new DefaultMutableTreeNode("B");
        DefaultMutableTreeNode c = new DefaultMutableTreeNode("C");

        DefaultMutableTreeNode aContact = new DefaultMutableTreeNode("Alice");
        DefaultMutableTreeNode bContact = new DefaultMutableTreeNode("Bob");
        DefaultMutableTreeNode cContact = new DefaultMutableTreeNode("Carol");

        root.add(a);
        root.add(b);
        root.add(c);

        a.add(aContact);
        b.add(bContact);
        c.add(cContact);

        JTree tree = new JTree(root);

        // Change the default JTree icons
        DefaultTreeCellRenderer renderer = (DefaultTreeCellRenderer) tree.getCellRenderer();
        Icon closedIcon = new ImageIcon(Objects.requireNonNull(
                this.getClass().getResource("/images/lightbulb_off.png")));
        Icon openIcon = new ImageIcon(Objects.requireNonNull(
                this.getClass().getResource("/images/lightbulb.png")));
        Icon leafIcon = new ImageIcon(Objects.requireNonNull(
                this.getClass().getResource("/images/lightning.png")));
        renderer.setClosedIcon(closedIcon);
        renderer.setOpenIcon(openIcon);
        renderer.setLeafIcon(leafIcon);

        JScrollPane pane = new JScrollPane(tree);
        pane.setPreferredSize(new Dimension(500, 500));

        getContentPane().add(tree);
    }
}

How do I remove JTree default icons?

By I Wayan Saryada in Swing 0 Comment

You can remove JTree default icons by modifying the tree cell renderer object. To get the cell renderer call the JTree.getCellRenderer() which will return a DefaultTreeCellRenderer object. Then you can remove the icon by setting a null value to the setLeafIcon(), setClosedIcon() and setOpenIcon().

package org.kodejava.swing;

import javax.swing.*;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeCellRenderer;
import java.awt.*;

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

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new JTreeRemoveIcon().setVisible(true));
    }

    private void initializeUI() {
        setSize(500, 500);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        DefaultMutableTreeNode root = new DefaultMutableTreeNode("Address Book");
        DefaultMutableTreeNode a = new DefaultMutableTreeNode("A");
        DefaultMutableTreeNode b = new DefaultMutableTreeNode("B");
        DefaultMutableTreeNode c = new DefaultMutableTreeNode("C");

        DefaultMutableTreeNode aContact = new DefaultMutableTreeNode("Alice");
        DefaultMutableTreeNode bContact = new DefaultMutableTreeNode("Bob");
        DefaultMutableTreeNode cContact = new DefaultMutableTreeNode("Carol");

        root.add(a);
        root.add(b);
        root.add(c);

        a.add(aContact);
        b.add(bContact);
        c.add(cContact);

        JTree tree = new JTree(root);

        // Remove default JTree icons
        DefaultTreeCellRenderer renderer = (DefaultTreeCellRenderer) tree.getCellRenderer();
        renderer.setLeafIcon(null);
        renderer.setClosedIcon(null);
        renderer.setOpenIcon(null);

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

        getContentPane().add(tree);
    }
}
Remove JTree Default Icon

Remove JTree Default Icon

How do I sort LinkedList elements?

By I Wayan Saryada in Core API, Util Package 0 Comment

To sort the elements of LinkedList we can use the Collections.sort(List<T> list) static methods. The default order of the sorting is a descending order.

package org.kodejava.util;

import java.util.LinkedList;
import java.util.Collections;

public class LinkedListSort {
    public static void main(String[] args) {
        LinkedList<String> grades = new LinkedList<>();
        grades.add("E");
        grades.add("C");
        grades.add("A");
        grades.add("F");
        grades.add("B");
        grades.add("D");

        System.out.println("Before sorting:");
        System.out.println("===============");
        for (String grade : grades) {
            System.out.println("Grade = " + grade);
        }

        // Sort the elements of linked list based on its data
        // natural order.
        Collections.sort(grades);

        System.out.println("After sorting:");
        System.out.println("===============");
        for (String grade : grades) {
            System.out.println("Grade = " + grade);
        }
    }
}

The result of the program are:

Before sorting:
===============
Grade = E
Grade = C
Grade = A
Grade = F
Grade = B
Grade = D
After sorting:
===============
Grade = A
Grade = B
Grade = C
Grade = D
Grade = E
Grade = F

How do I get the first and the last element of a LinkedList?

By I Wayan Saryada in Core API, Util Package 0 Comment

The get the first element we can use the LinkedList.getFirst() method and to get the last element we can use the LinkedList.getLast() method.

package org.kodejava.util;

import java.util.LinkedList;

public class LinkedListGetFirstLast {
    public static void main(String[] args) {
        LinkedList<String> names = new LinkedList<>();
        names.add("Alice");
        names.add("Bob");
        names.add("Carol");
        names.add("Mallory");

        // Get the first and the last element of the linked list
        String first = names.getFirst();
        String last = names.getLast();

        System.out.println("First member = " + first);
        System.out.println("Last member  = " + last);
    }
}

The program will print the following result:

First member = Alice
Last member  = Mallory

How do I reverse the order of LinkedList elements?

By I Wayan Saryada in Core API, Util Package 0 Comment

To reverse the order of LinkedList elements we can use the reverse(List<?> list) static method of java.util.Collections class. Here is the example:

package org.kodejava.util;

import java.util.LinkedList;
import java.util.Collections;

public class LinkedListReverseOrder {
    public static void main(String[] args) {
        LinkedList<String> grades = new LinkedList<>();
        grades.add("A");
        grades.add("B");
        grades.add("C");
        grades.add("D");
        grades.add("E");
        grades.add("F");

        System.out.println("Output in original order:");
        System.out.println("=========================");
        for (String grade : grades) {
            System.out.println("Grade = " + grade);
        }

        // Reverse the element order in the linked list object.
        Collections.reverse(grades);

        System.out.println("Output in reverse order:");
        System.out.println("=========================");
        for (String grade : grades) {
            System.out.println("Grade = " + grade);
        }
    }
}

Here is the output of the program:

Output in original order:
=========================
Grade = A
Grade = B
Grade = C
Grade = D
Grade = E
Grade = F
Output in reverse order:
=========================
Grade = F
Grade = E
Grade = D
Grade = C
Grade = B
Grade = A