Geir Magnusson Jr. wrote:
1) Are there other models? How do some of the commercial VMs do it?
Sun are generally using two different approaches:
- package private classes in the common java.* and javax.* packages,
which are protected from external usage by the language protection model
- proprietary classes in the com.sun.* and sun.* packages, which are in
theory accessible to application programmers, but should only be used
through the java.* and javax.* APIs to avoid dependencies to a specific
VM implementation
I think both approaches are completely valid and there is no need to
enforce a specific way to do this. The first possibility has the
disadvantage you mention, that Harmony may decide to implement an
internal class java.lang.Foo and Sun decides to add a new class
java.lang.Foo to the next Java version. The second possibility has the
advantage, that you are in full control of what recides in the
org.apache.harmony packages, but the disadvantage that a programmer may
decide to actually use these classes and hence make his program
dependent on the Harmony VM implementation. Unfortunately, some Apache
software actually does rely on com.sun classes, e.g. the SSL connectors
in Tomcat.
Tor
