We will use the following meta-custom/recipes-java/java-helloworld/java-helloworld-1.0/HelloWorldSwing.java graphical Swing hello world example:

import javax.swing.JFrame; 
import javax.swing.JLabel; 
 
public class HelloWorldSwing { 
    private static void createAndShowGUI() { 
        JFrame frame = new JFrame("Hello World!"); 
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
 
        JLabel label = new JLabel("Hello World!"); 
        frame.getContentPane().add(label); 
 
        frame.pack(); 
        frame.setVisible(true); 
    } 
 
    public static void main(String[] args) { 
        javax.swing.SwingUtilities.invokeLater(new Runnable() { 
            public void run() { 
                createAndShowGUI(); 
            } 
        }); 
    } 
} 

To integrate this HelloWorldSwing application, we can use a Yocto meta-custom/recipes-java/java-helloworld/java-helloworld_1.0.bb recipe, as follows:

DESCRIPTION = "Simple Java Swing hello world application" 
SECTION = "examples" 
LICENSE = "MIT" 
LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4 
   f302" 
 
RDEPENDS_${PN} = "java2-runtime" 
 
SRC_URI = "file://HelloWorldSwing.java" 
 
S = "${WORKDIR}" 
 
inherit java-library 
 
do_compile() { 
        mkdir -p build 
        javac -d build `find . -name "*.java"` 
        fastjar cf ${JARFILENAME} -C build . 
} 
 
BBCLASSEXTEND = "native" 

The recipe is also buildable for the host native architecture. We can do this either by providing a separate java-helloworld-native recipe that inherits the native class or by using the BBCLASSEXTEND variable as we did earlier. In both cases, we could then use the _class-native and _class-target overrides to differentiate between native and target functionality. Even though Java is byte-compiled and the compiled class will be the same for both, it still makes sense to add the native support explicitly.