effective ways to use abstraction in programming code example

Example: how do you implement abstraction in your framework

I have created my PageBase class as super
class of the all page classes. 
I have collected all common elements
and functions into PageBase class and
all other page classes extent PageBase class.
By doing so, I don't have to locate very
common WebElements and it provides
reusability in my framework.

I  have implement abstraction in my POJO
classes for API Testing. My POJO classes
implements Comparable interface and
I override the compareTo() abstract method. 

These concepts are commonly used in
  framework development. Abstract class
    is used in defining a common super
class while writing Page Object Model 
layer of the framework. We usually create 
an abstract class named PageBase to have
all common members for every page written 
in this class for example getPageTitle(). 
Then each Page class 
  (HomePage, LoginPage, DashboardPage etc.)
inherit from BasePage. Sometimes one
may need to change the behavior of 
methods implemented in superclass. 
So, subclass has freedom to override 
that method where we use polymorphism. 
This is how we use Abstract class in projects.