One of the oldest and most proven programming languages in the world. Java is used exclusively for object-oriented programming. It is characterized by classes, exceptions, constructors, that must be closely monitored. In addition, it is necessary to think about the logic in advance. Despite its complexity, the language is actively used by Android developers. Undoubtedly, Java is one of the most powerful and functional languages, which is ideal for the most complex tasks and projects for Android mobile applications.