Javadoc
Constant (unmodifiable) interface for dVector3.
This returns an unmodifiable view of an (most likely) modifiable object.
WARNING: This is only unmodifiable for the user. The class that returned
this object may continue to modify it, these changes will also reflect in
the 'unmodifiable view' that the user has.
If the user requires a lasting immutable object, then the object needs to
be cloned.
This interface should only be implemented by DVector3.
This allows efficient optimisation by the JVM, which is not
possible with 2 (still somewhat efficient) or more (slow)
sub-classes.