The default JDK has provided a few subclass of LookAndFeel that you can use as the argument
to setLookAndFeel.
com.sun.java.swing.plaf.gtk.GTKLookAndFeel
javax.swing.plaf.metal.MetalLookAndFeel
com.sun.java.swing.plaf.windows.WindowsLookAndFeel
com.sun.java.swing.plaf.motif.MotifLookAndFeel
For instance, the following code forces the application to use the Motif look and feel.
UIManager.setLookAndFeel ("com.sun.java.swing.plaf.motif.MotifLookAndFeel");