A few times during development of the J2SE 1.5 release the Tools and Libraries
team has attempted to make modifications to certain core classes and found that
HotSpot has hardcoded offsets to these classes' fields in javaClasses.cpp and
that modification of the classes causes VM startup to fail. These hardcoded
offsets should be changed to be computed at run time in the 1.5.1 release (and
any startup time impact measured before putting back these changes). It is
likely that some primordial offsets will have to remain but the bulk of them
should be able to be converted.