Swing Looks ...Great (Part III Nimbus) 📎
Nimbus doesn't have to be installed, it is shipped with JDK 1.6. You only have to activate it.
There is a hacky (because of reflection) but robust way to activate that. This complex approach is needed, because Nimbus was introduced with JDK 1.6u10 and was not available before.
try {
    for (LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
        if ("Nimbus".equals(info.getName())) {
            UIManager.setLookAndFeel(info.getClassName());
            break;
        }
    }
} catch (UnsupportedLookAndFeelException e) {
    // handle exception
} catch (ClassNotFoundException e) {
    // handle exception
} catch (InstantiationException e) {
    // handle exception
} catch (IllegalAccessException e) {
    // handle exception
}
[Code Snippet from:http://download.oracle.com/javase/6/docs/technotes/guides/jweb/otherFeatures/nimbus_laf.html]
The command line option
-Dswing.defaultlaf=com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel can be used as well.With NetBeans you can create a Nimbus mock-up in minutes (actually seconds).