Where to use abstraction java code example

Example 1: abstraction in java

Abstraction is defined as hiding internal implementation and showing only 
necessary information.
// abstract class
abstract class Addition
{
   // abstract methods
   public abstract int addTwoNumbers(int number1, int number2);
   public abstract int addFourNumbers(int number1, int number2, int number3, int number4);
   // non-abstract method
   public void printValues()
   {
      System.out.println("abstract class printValues() method");
   }
}
class AbstractMethodExample extends Addition
{
   public int addTwoNumbers(int number1, int number2)
   {
      return number1 + number2;
   }
   public int addFourNumbers(int number1, int number2, int number3, int number4)
   {
      return number1 + number2 + number3 + number4;
   }
   public static void main(String[] args)
   {
      Addition add = new AbstractMethodExample();
      System.out.println(add.addTwoNumbers(6, 6));
      System.out.println(add.addFourNumbers(8, 8, 3, 2));
      add.printValues();
   }
}

Example 2: abstraction example in java

In my framework I have achieved abstraction 
by using collections or Map, because it’s all interface. 
  Most of the cases I come   across using List. 
  If we want to access elements frequently by using index, 
List is a way to go. ArrayList provides faster access if we know index. 
  If we want to store elements and want them to maintain an order, 
List is a better choice. 
i) List webs = driver.getWindowHandles(); 
=>create a list first to store web URLs in list
ii) findElements evaluates multiple elements 
so therefore will assigned to List 
iii) To handle dynamic elements store it in the list and identify by index: 
List all = driver.findElements(By.tagname(“”));
In my framework I follow POM and had situations 
where some pages shared similar actions that were similar 
but worked slightly different, so I was able to use abstraction 
to define those actions and implement them in each page according 
to what was needed for that webpage