The structure of Android's Java code
In addition to these resources, it is worth noting that Java as used in Android has a structure to its code. There are many millions of lines of code that we can take advantage of. This code will obviously need to be organized in a way that makes it easy to find and refer to. It is organized into packages that are specific to Android.
Packages
Whenever we create a new Android app, we will choose a unique name known as a package. We will see how we do this in the Building our first Android app section. Packages are often separated into sub-packages, so they can be grouped together with other similar packages. We can simply think of this as folders and sub-folders, which is almost exactly what it is.
We can think of all the packages that the Android API makes available to us as code from a code library. Some common Android packages we will use include the following:
android.graphicsandroid.databaseandroid.view.animation...
