Immutability for array members thru Arrays.copyOf. See Josh Bloch, Effective Java, Item 12: Minimize the accessibility of classes and members
Not needed imports
Unneeded imports
Introduced final
Making more clear the immutability in javadoc
Multiple null pointer checks and javadocs for null pointer exceptions.
See Josh Bloch, Effective Java, Item 23: Check parameters for validity.
Unused import
Not exposing the array for writing by using a copy.
Indention fix
Returning of valid NULL values (would be better to have zero sized arrays)
Moved NULL values to ZERO sized array as proposed by Josh Bloch, Item 27: Return zero-length arrays, not nulls.
Actually in CmdLineParser there were some accesses to the fields that could be null without null pointer checks.
Merge pull request #67 from sfuhrm/code-cleanups

Code cleanups