One of my friends complained that we pay too much attention to the
"trivial things" and wished us to discuss some "advanced" topics.
To respond, I asked some questions here. Hope people can contribute ideas and thoughts.

1) What is java.lang.ThreadLocal for?
2) There is a package called java.lang.ref, under which there are a few classes and references, for exapmle, java.lanag.ref.WeekRefernce.
What is this for?
3) In Enterprise JavaBeans API, the getEnvironment() method of javax.ejb.EJBObject jas been deprecated. How the similar functionality is
implemented in EJB API now?

Thanks for contributions.