private void initResourceBundle( UIDefaults defaults, String bundleName ) {
		// add resource bundle for localized texts
		defaults.addResourceBundle( bundleName );

		// Check whether Swing can not load the FlatLaf resource bundle,
		// which can happen in applications that use some plugin system
		// and load FlatLaf in a plugin that uses its own classloader.
		// (e.g. Apache NetBeans)
		if( defaults.get( "TabbedPane.moreTabsButtonToolTipText" ) != null )
			return;

		// load FlatLaf resource bundle and add content to defaults
		try {
			ResourceBundle bundle = ResourceBundle.getBundle( bundleName, defaults.getDefaultLocale() );

			Enumeration<String> keys = bundle.getKeys();
			while( keys.hasMoreElements() ) {
				String key = keys.nextElement();
				String value = bundle.getString( key );

				String baseKey = StringUtils.removeTrailing( key, ".textAndMnemonic" );
				if( baseKey != key ) {
					String text = value.replace( "&", "" );
					String mnemonic = null;
					int index = value.indexOf( '&' );
					if( index >= 0 )
						mnemonic = Integer.toString( Character.toUpperCase( value.charAt( index + 1 ) ) );

					defaults.put( baseKey + "Text", text );
					if( mnemonic != null )
						defaults.put( baseKey + "Mnemonic", mnemonic );
				} else
					defaults.put( key, value );
			}
		} catch( MissingResourceException ex ) {
			LoggingFacade.INSTANCE.logSevere( null, ex );
		}
	}
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