IV. ANDROID APPLICATION COMPONENT
A core feature of Android is that one application could
use component element that belong to another application (if
the component is permitted using). In order to achieve such
functions, Android system must launch the application while
any part of the application is asked and instantiate Java
objects that being asked. Unlike most operating system, there
is no single point that the system can enter in an Android
application (for example, there no main ( ) function in an
Android application). Instead, each component is a different