public interface MenuBarEntryProvider {
    public Optional<List<MenuItem>> getMenuItems();
	public MenuBarParentMenu getMenuExtensionParent();
 }

Note that this interface will likely change in future releases of the IGB API. The getParentMenuName method will likely a custom enum type and not a String literal.  Additionally, we will add "weight" as an attribute to our custom JMenuItem class.  So it is likely this interface will ultimately contain one simple getMenuItem() method.  

Creating a new Java class (MenuBarExtensionExample)

Within NetBeans, check that your IGB Menubar Extension project is the currently selected project - the name of the currently opened project is shown on the NetBeans title bar. If it isn't, select File > Open Project to open it.

Next, create a new Java class named IgbToobarExtension:

• Select File > New File
• Under Choose File Type, select Java
• Select Next
• Enter class Name MenuBarExtensionExample
• Select package org.lorainelab.igb.menu.api.example
• Select Finish

package org.lorainelab.igb.menu.api.example;
import aQute.bnd.annotation.component.Component;
import java.util.Arrays;
import java.util.List;
import java.util.Optional;
import javax.swing.JOptionPane;
import org.lorainelab.igb.menu.api.MenuBarEntryProvider;
import org.lorainelab.igb.menu.api.model.MenuBarParentMenu;
import org.lorainelab.igb.menu.api.model.MenuItem;
@Component(immediate = true)
public class MenuBarExtensionExample implements MenuBarEntryProvider {

    @Override
    public Optional<List<MenuItem>> getMenuItems() {
        MenuItem menuItem = new MenuItem("Hello World App", (Void t) -> {
            JOptionPane.showMessageDialog(null, "Hello IGB World!");
            return t;
        });
        menuItem.setWeight(1000000000);
        return Optional.ofNullable(Arrays.asList(menuItem));
    }

    @Override
    public MenuBarParentMenu getMenuExtensionParent() {
        return MenuBarParentMenu.TOOLS;
    }
}

About the implementation class

The @Component annotation 

@Component(name = IgbToolbarExtension.COMPONENT_NAME, immediate = true, provide = IgbMenuItemProvider.class)
public class IgbToolbarExtension implements IgbMenuItemProvider {...}

This annotation is processed by the felix maven-bundle-plugin (BND) and declares that the OSGi runtime will manage creation and destruction of any instances of this class. This is an important point to understand about how OSGi-based applicaitions function. Your code will not directly manage the life cycle of your class. Instead, you specify the behavior and lifecycle of your objects using annotations.

The immediate=true annotation attribute specifies to the OSGi runtime that this component should be instantiated immediately instead of lazily. 

See http://www.aqute.biz/Bnd/Components for more information about the annotation attributes.

The LogEventAction

When a user selects your new menu item, this action will execute. Note it prints a message to the IGB console. Note also that it uses the SLF4j API to log events to the IGB console.