How to set dock icon of Java application

This solution is only available from JDK 9.

In other to set the JDK version on NetBeans, right click on Project > “Properties” >> “Sources” > “Source/Binary format”; and “Libraries” > “Java Platform”.

package main;

import javax.swing.JFrame;
import javax.swing.JLabel;
import java.awt.Image;
import java.awt.Taskbar;
import java.awt.Toolkit;
import java.net.URL;

/**
 * author: flohall
 * date: 2019-07-07
 */
public final class Main {

    public static void main (String[] args){

        final JFrame jFrame = new JFrame();

        //loading an image from a file
        final Toolkit defaultToolkit = Toolkit.getDefaultToolkit();
        final URL imageResource = Main.class.getClassLoader().getResource("resources/images/icon.gif");
        final Image image = defaultToolkit.getImage(imageResource);

        //this is new since JDK 9
        final Taskbar taskbar = Taskbar.getTaskbar();

        try {
            //set icon for mac os (and other systems which do support this method)
            taskbar.setIconImage(image);
        } catch (final UnsupportedOperationException e) {
            System.out.println("The os does not support: 'taskbar.setIconImage'");
        } catch (final SecurityException e) {
            System.out.println("There was a security exception for: 'taskbar.setIconImage'");
        }

        //set icon for windows os (and other systems which do support this method)
        jFrame.setIconImage(image);

        //adding something to the window so it does show up
        jFrame.getContentPane().add(new JLabel("Hello World"));

        //some default JFrame things
        jFrame.setDefaultCloseOperation(jFrame.EXIT_ON_CLOSE);
        jFrame.pack();
        jFrame.setVisible(true);
    }
}

External References

• “How do you change the Dock Icon of a Java program?“, by flohall on stackoverflow
• “JEP 272: Platform-Specific Desktop Features“, OpenJDK