Sun changed swing naming convention from com.sun.java.swing to javax.swing.This created a bit of confusion, but you can exploit it to see what versionof swing is installed in a browser, or any other Java enabled environment.

 Class swingNewJButtonClass = null;Class swingOldJButtonClass = null;try {    swingOldJButtonClass = Class.forName("com.sun.java.swing.JButton");    if(swingOldJButtonClass != null)        System.out.println("Old Version of Swing installed"); }catch(ClassNotFoundException e) {}try {    swingNewJButtonClass = Class.forName("javax.swing.JButton");    if(swingNewJButtonClass != null)        System.out.println("New Version of Swing installed"); } catch(ClassNotFoundException e) {}if(swingOldJButtonClass == null && swingNewJButtonClass == null)    System.out.println("No Version of Swing Installed");