private void initializeAqua() {
		if( aquaLoaded )
			return;

		aquaLoaded = true;

		// create macOS Aqua LaF
		String aquaLafClassName = "com.apple.laf.AquaLookAndFeel";
		BasicLookAndFeel aquaLaf;
		try {
			if( SystemInfo.isJava_9_orLater ) {
				Method m = UIManager.class.getMethod( "createLookAndFeel", String.class );
				aquaLaf = (BasicLookAndFeel) m.invoke( null, "Mac OS X" );
			} else
				aquaLaf = Class.forName( aquaLafClassName ).asSubclass( BasicLookAndFeel.class ).getDeclaredConstructor().newInstance();
		} catch( Exception ex ) {
			LoggingFacade.INSTANCE.logSevere( "FlatLaf: Failed to initialize Aqua look and feel '" + aquaLafClassName + "'.", ex );
			throw new IllegalStateException();
		}

		// remember popup factory because aquaLaf.initialize() installs its own
		// factory, which makes sub-menu rendering "jittery"
		PopupFactory oldPopupFactory = PopupFactory.getSharedInstance();

		// initialize Aqua LaF
		aquaLaf.initialize();
		aquaLaf.uninitialize();

		// restore popup factory
		PopupFactory.setSharedInstance( oldPopupFactory );
	}
Initialize Aqua LaF on macOS, which is required for using Mac screen menubar.
(at least on Java 8, since 9 it seems to work without it)
<p>
This loads the native library "osxui" and initializes JRSUI.
Because both are not unloaded/uninitialized, Aqua LaF is initialized only once.
flatlaf-core/src/main/java/com/formdev/flatlaf/FlatLaf.java