There is no good reason to have a mutable object as the ``++public++`` (by default), ``++static++`` member of an ``++interface++``. Such variables should be moved into classes and their visibility lowered. 


Similarly, mutable ``++static++`` members of classes and enumerations which are accessed directly, rather than through getters and setters, should be protected to the degree possible. That can be done by reducing visibility or making the field ``++final++`` if appropriate. 


Note that making a mutable field, such as an array, ``++final++`` will keep the variable from being reassigned, but doing so has no effect on the mutability of the internal state of the array (i.e. it doesn't accomplish the goal).


This rule raises issues for ``++public static++`` array, ``++Collection++``, ``++Date++``, and ``++awt.Point++`` members.
