Answers for "what is java abstraction"

abstraction java

bstraction: Hiding the implementation details, 
concentrating on essentials things, 
without worrying about the details 
■ In java, abstraction is achieved via abstract class or interface 
■ Abstraction cannot exist without inheritance 

3.1. Abstract class a class that's meant to be inherited 
(cannot be private or final)
■ To create an abstract class: add keyword abstract 
before the class declaration 
■ A class that we cannot create object 
when abstract class extended by regular class: 
we MUST override all the abstract methods of super class
when abstract class extended by abstract class: 
no need to override any abstract methods

abstract class vs non-abstract class:
NON-ABSTRACT CLASS:
cannot have: abstract methods
can have: constructor, instance method, static method, 
instance block, static block, instance variable, static variable
ABSTRACT CLASS:
can have: constructor, instance method, static method, instance block,
static block, instance variable, static variable...
ABSTRACT METHOD: method without implementation, meant to be override 
(cannot create object, cannot be final,static,private)

FRAMEWORK EXAMPLE:
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)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

Abstraction in java

// abstraction in java with example
// 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();
   }
}

Abstraction in java

// example on abstract class in java
import java.util.*;
// abstract class
abstract class Shape
{
   // abstract method
   abstract void sides();
}
class Triangle extends Shape
{
   void sides()
   {
      System.out.println("Triangle shape has three sides.");
   }
}
class Pentagon extends Shape
{
   void sides()
   {
      System.out.println("Pentagon shape has five sides.");
   }
   public static void main(String[] args)
   {
      Triangle obj1 = new Triangle();
      obj1.sides();
      Pentagon obj2 = new Pentagon();
      obj2.sides();
   }
}