How Java and Android work together

Before we start our Android quest, we need to understand how Android and Java work together.

Android is a complex system, but you do not need to understand it in depth in order to make amazing apps.

After we write a program, in Java, for Android, we click on a button, and our code is transformed into another form – the form that is understood by Android. This other form is called bytecode, and the transformation process is called compiling. The reason you can use the Kotlin programming language to write Android apps is that it directly compiles to the same bytecode as Java. In fact, Java can be translated to Kotlin with the click of a button.

Then, when the user installs our application, the bytecode is translated by another process, known as the Android Runtime (ART), into machine code. This is the fastest possible execution format. So, if you have ever heard people saying that you shouldn't use Java because it is slow, then...