This week's book giveaway is in the Reactive Progamming forum. We're giving away four copies of Reactive Streams in Java: Concurrency with RxJava, Reactor, and Akka Streams and have Adam Davis on-line! See this thread for details.
emma roberts wrote:but what I can not understand why the increment in the signature method change the value of the i but normally all change in the signature method and body is not considered outside the addTwo
What are you referring to as the "signature method"? It's not clear what you're confused about. Was there something in Dave's explanation that you did not understand?