Minor improvements java comments.
Fix: Class DuplicatedDigitsException  changed to DuplicatedDigitException.
Unnecessary constructor removed.
Some minor reviews.
Important enhancement in documentation.
Enhancement in java comments.
Enhancement in java comments.
Enhancement in java comments.
Enhancement in java comments.
Enhancement in java comments.
Unnecessary imports removed.
Change types 'Boolean' to its primitive 'boolean'.
Enhancement in java comments & refactoring.
Minor code improvements.
Enhancement in java comments.
Code reviewed.
Enhancement in java comments & code refactoring.
Enhancement in java comments.
Enhancement in java comments.
Code reviewed.