Exercise from London Software Craftsmanship Community meetup, Functional programming techniques in object-oriented languages (http://www.meetup.com/london-software-craftsmanship/events/38306082/).

There were few rules to follow:
1. No mutable objects (yours or libraries). All classes must have entirely immutable fields.
2. Methods must end by returning.
3. All other statements in a method must be assignment to new (final) variables.
4. No conditionals or loops (with the exception of the ternary-style if).
5. Write OO code.

Tasks were:
1. To find a Jack in a hand of cards.
2. Find out if there is a pair (any pair) in a hand.