 #6323 Java 8 version for Problem-Solving-Examples-in-RxJava (#6324)
 #6323 Java 8 version for Problem-Solving-Examples-in-RxJava (#6324)

* #6323 Java 8 version for Project Euler problem

* #6323 Java 8 version for Generate the Fibonacci Sequence

* #6323 Java 8 version for Project Euler problem
 - Fix name of variable

* #6324 Fixing for code review.

reactivex/rxjava,ReactiveX/RxJava,reactivex/rxjava,ReactiveX/RxJava,NiteshKant/RxJava,artem-zinnatullin/RxJava,artem-zinnatullin/RxJava,NiteshKant/RxJava