Explanation/Reference:
The following is a list of Java features that you should avoid, hence restricting their use in your EJB components' implementation code:
(A) Loading native libraries.
(C) Attempting to create or obtain a class loader, set or create a new security manager (C), stop the JVM, change the input, output, and error streams. That restriction enforces security and maintains the EJB container's ability to manage the runtime environment.
(not B) Using static, nonfinal fields. Declaring all static fields in the EJB component as final is recommended. That ensures consistent runtime semantics so that EJB containers have the flexibility to distribute instances across multiple JVMs.
Reference: Programming restrictions on EJB