Which language i learn to build a android app. Example whatsapp

Answer 1

Well, it depends there is many languages that can do this but for example Whatsapp was written with a mix of languages most noticable is Erlang.

For mobile development I would reccomend any the following;
Java, C++, Swift(primarily apple), C and even Python or C#

Chances are that you might want to use several depending on the type of apps you create.

To answer Wen Qin's reply, C++ can be needed to interact on a lower level that is harder to with the languages you mention, and it's also a preference. The answer is good but you shouldn't tell anyone to NEVER use a language.

Answer 2

For android, you most likely would want to use Lua or Java. C# is fine if you are building small applications. NEVER use C++, it gives you headache while trying to crossplatform it.(I mean Java/Lua exists, why torture yourself with C++?)

Answer 3

For Android you need to learn Java.

Answer 4

Cup of java