Instrumenting java core libraries

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开发者_运维知识库 find branch coverage of some java core libraries. The tool I am using for branch coverage actually instruments the .class files.

Thanks

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

Sure, it's right there, in jre/lib/rt.jar inside your JAVA_HOME

Yes, the class files are inside the #{JDK INSTALL PATH}/jre/lib/rt.jar archive. Or if you use an IDE like Eclipse you can ctrl+click on any string method, or on "String" in declarations like private String var; to open that class.