How to find file path of a Java API class?

Question

In particular - the Applet.class. How could I find where it locally resides? I have tried the following, but I get an exception:

 System.out.println(JApplet.class.getProtectionDomain().getCodeSource().getLocation().getPath());

It is of course somewhere in Program Files/Java/jdk_7_xx/ but I have had quite a look around and searched online and cannot find the answer. I have always wondered where specific classes reside on the system.

Note: If you want some more detail (not necessary to read below this):

What I specifically want to do is edit the Applet.class and point my Eclipse to a new JRE System Library that contains the edited Applet.class. In theory this sounds plausible, yet in practice I am unsure.

This is needed so I can test legacy code which keeps making calls to super methods - I have tried many frameworks/approaches and tried multiple possible solutions that have been posted on stack overflow and other online resources - none work.

Answer 1

Found the JApplet.class in C:\\Program Files (x86)\\Java\\jdk1.7.0_25\\jre\\lib\\rt.jar

Made a back-up of jdk1.7.0.25 on my desktop and put it in a folder Desktop\\BACKUP\\jdk1.7.0.25

Unzipped it (rt.jar), decompiled Applet.class with jad, changed some methods and even added a new one, recompiled it, rezipped it, replaced the old rt.jar with the new one, made a new eclipse project and made it use the JRE in Desktop\\BACKUP\\jdk1.7.0.25 and it worked perfectly.

Answer 2

..do you know how I can find the specific path of the Applet.class?

For your own PC? Sure. For the PC of a client of your applet? No.

In fact, Oracle (or was it Sun?) eventually decided it was not the business of an app. launched within the Java Plug-In (eg applets or JWS apps), to know where the classes were cached. Not even it that app. was fully trusted.

I'm assuming its in a jar somewhere?

Don't assume. It is set in the Java Control Panel, which defaults to 'no compression'.