The example below shows how to use GTKLookAndFeel in Swing applications.
Java Code:
try {
 // sure look and feel
 UIManager.setLookAndFeel("com.sun.java.swing.plaf.gtk.GTKLookAndFeel");
 
 // not-so-sure look and feel
 System.setProperty("os.name", "Windows");
 System.setProperty("os.version", "5.1");
 UIManager.setLookAndFeel(
   "com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
 } 
catch (Exception ex) {
 ex.printStackTrace();
}