Adding new method into String.java (just for personal usage)

Question

For some reason, it kept bringing in the old String.class, even I updated it the rt.jar with the new String.class. I even checked it with jar -tvf rt.jar. It has the new String.class. However, it seemed to constantly loading in the old one. Unless I use bootclasspath. The followng is the test :
1.     I add a new function to String.java
a.     : goody() { return “this is a test method”; }
2.     To compile:
a.     javac -bootclasspath ".\;C:\Program Files\Java\jdk1.6.0_03\jre\lib\rt.jar" String.java
jar uf rt.jar java/lang/String.class
3.     To test with file test.java where it calls String.goody()
a.     To make sure it is not pulling in old code, I had to copy the new rt.jar to my test directory:
i.     copy "C:\Program Files\Java\jdk1.6.0_03\jre\lib\rt.jar” .\
4.     compile my test.java:
a.     javac -bootclasspath .\rt.jar test.java
5.     Execute the jvm:
a.     java -Xbootclasspath:.\rt.jar;.\; test
6.     I got output : “this is test method”
=========================
if I use the regular : java classpath where the new classpath does indeed reside in, it claims the symbol not found. I have to copy the rt.jar to my local and use -Xbootclasspath. Suggestion? Or, this is really the only way to be able to call a new method installed in String.class?

Answer 1

eproflab wrote:
a.     To make sure it is not pulling in old code, I had to copy the new rt.jar to my test directory:
i.     copy "C:\Program Files\Java\jdk1.6.0_03\jre\lib\rt.jar” .\That will not work.
You must replace it in the VM directory or use the bootpath options. There is no other way.
Note that you mess up with what you are doing (replacing the rt.jar way) that not only will you not be able to run, not even to get an exception, but you will not be able to compile either.