Skip to main content

Inheritance

Logging frameworks like Log4J allow us to send logs to a multitude of destinations. The code responsible for logging to a destination is usually encapsulated into separate classes.






Without inheritance



With inheritance




When to use inheritance:

  • IS-A relationship
    • An Employee is a Person
    • A BumperSale is a Sale
    • A Square is a Shape
  • IS-LIKE-A relationship

But if the relationship between them is HAS-A (eg: Car has an Engine), then we use composition instead of inheritance.


Reflections:


What is the relationship between the following objects?

  • Bathroom - Bathtub
  • Car - Engine
  • Person - Professor
  • Vehicle - Car

Note: This post was originally posted on my blog at http://www.adaptivelearningonline.net

Comments

Popular posts from this blog

My HSQLDB schema inspection story

This is a simple story of my need to inspect the schema of an HSQLDB database for a participar FOREIGN KEY, and the interesting things I had to do to actually inspect it. I am using an HSQLDB 1.8 database in one of my web applications. The application has been developed using the Play framework , which by default uses JPA and Hibernate . A few days back, I wanted to inspect the schema which Hibernate had created for one of my model objects. I started the HSQLDB database on my local machine, and then started the database manager with the following command java -cp ./hsqldb-1.8.0.7.jar org.hsqldb.util.DatabaseManagerSwing When I tried the view the schema of my table, it showed me the columns and column types on that table, but it did not show me columns were FOREIGN KEYs. Image 1: Table schema as shown by HSQLDB's database manager I decided to search on StackOverflow and find out how I could view the full schema of the table in question. I got a few hints, and they all pointed to

Fuctional Programming Principles in Scala - Getting Started

Sometime back I registered for the Functional Programming Principles in Scala , on Coursera. I have been meaning to learn Scala from a while, but have been putting it on the back burner because of other commitments. But  when I saw this course being offered by Martin Odersky, on Coursera , I just had to enroll in it. This course is a 7 week course. I will blog my learning experience and notes here for the next seven weeks (well actually six, since the course started on Sept 18th). The first step was to install the required tools: JDK - Since this is my work machine, I already have a couple of JDK's installed SBT - SBT is the Scala Build Tool. Even though I have not looked into it in detail, it seems like a replacement for Maven. I am sure we will use it for several things, however upto now I only know about two uses for it - to submit assignments (which must be a feature added by the course team), and to start the Scala console. Installed sbt from here , and added the path

Five Reasons Why Your Product Needs an Awesome User Guide

Photo Credit: Peter Merholz ( Creative Commons 2.0 SA License ) A user guide is essentially a book-length document containing instructions for installing, using or troubleshooting a hardware or software product. A user guide can be very brief - for example, only 10 or 20 pages or it can be a full-length book of 200 pages or more. -- prismnet.com As engineers, we give a lot of importance to product design, architecture, code quality, and UX. However, when it comes to the user manual, we often only manage to pay lip service. This is not good. A usable manual is as important as usable software because it is the first line of help for the user and the first line of customer service for the organization. Any organization that prides itself on great customer service must have an awesome user manual for the product. In the spirit of listicles - here are at least five reasons why you should have an awesome user manual! Enhance User Satisfaction In my fourteen years as a