I can't realize how android devices are able to be sold having iPad is in the market.

Uncle Bob summarizes the latest research in the field of software architecture (Ports and Adapters (GOOS), DCI by Coplien etc): The Clean Architecture

"...things such as functions and methods look essentially the same, but they derive from very different ideas. A method reflects a behavior expected in the domain, and a function reflects a unit of execution in the machine. A message and a function call might be identical, in syntax and in how they are implemented inside a machine. But who sends the message to whom, how that message is interpreted, and what kind of code will be necessary to respond will be quite different."— David West, "Object Thinking"

"When the guidance comes from someone who is a genuine Master programmer, then it’s possible he/she is trying to show us something we don’t even know we don’t know. How can we find out, other than by exploring the suggested path?" Why should we do code katas.