Instrumenting java core libraries

Question

When we compile a java program, we get .class files. Can I access these .class files of java core libraries? e.g. can I have access to java.lang.String.class ?

Actually I am doing a research and trying to find branch coverage of some java core libraries. The tool I am using for branch coverage actually instruments the .class files.

Thanks

Answer 1

It's in rt.jar in your JRE directory. You've even got the sources in src.zip. (Or you could just pull the latest version of OpenJDK.)

Also, if you want to instrument the base classes, you'll also need to specify a boot classpath. Look at the -Xbootclasspath option for java: http://java.sun.com/javase/6/docs/technotes/tools/windows/java.html