I'm using the follwoing code and calling it in an applet. It used to work completely fine when I used with browser with JRE 6 Update 21. However, the code is now returning null for all browsers that support JRE 6 Update 22. Here is the code -
What does it print if you try that code on a command line? I tried it (after removing the remaining call to checkValidMAC), and the only null MAC address was that of my "lo" adapter - which is the loopback adapter, and not really a physical device.
Again, if I run that code after changing line 43, I see all my network adapters - lo, two VMware virtual adapters and my actual network adapter (well, the one that isn't disabled - I have two). The MAC address (LAN ID) printed at the bottom is my actual MAC address. So I'll ask you again - what is the output when you run it?
Never, never write == false or == true.
Those lines with multiple || checks are too long to read; they ought to have newlines in to break them up.
The multiple || look very inelegant. See if you can create a regular expression to match the multiple possibilities.
With a little knowledge, a cast iron skillet is non-stick and lasts a lifetime.