The structure here I describe globally. In any programming, there are rules of its own, for example, the modifier permissions. In short, the modifier permissions are public, private and protected. The early programmer’s mistake did not understand all three, they originally wrote as important as the road program. In the meantime, you can go to inixindojogja.co.id/events/android-programming-android-studio/ if you’re looking for an excellent Andriod programmer training.
Indeed the effect is not visible when you use only for the college assignment, but it will be seen when you have made a big project, there will be seen how important the modifier access rights.
Learn also about OOP (Object Oriented Programming), OOP is a bit complex when just learning, but it will help you write the more structured program and easy to understand when opened again.
most people I meet do not have any plans for making the program. For example, get a college assignment to create a login program, they just search the source code on the internet, what he got it taken, why not you modification, from the originally proceded to be oriented. It really helps you in logic programming.
Learn the Method carefully, Learn how OOP is not just theory but should practice coding.