Notes on "Head First: Object-Oriented Analysis & Design" - Chapter 1

Jul 24th, 2020

These are my notes for the book Head First: Object-Oriented Analysis & Design. Information provided here originates from the the book (and therefor the authors who wrote it). I highly, highly recommend getting the book yourself and reading it fully. This is just the information that I felt was most important for myself. The coding problems and exercises they provide are worthwhile, and should be a good enough reason to purchase it.


  • Flexibility - Used so that your software can change and grow without constant rework. I keep your application from being fragile.
  • Encapsulation - Used to keep the parts of your code that stay the same separate from the parts that change; then it's really easy to make changes to your code without breaking everything.
  • Functionality - Without me, you'll never actually make the customer happy. No matter how well-designed your application is, I'm the thing that puts a smile on the customer's face.
  • Design Pattern - All about reuse and making sure you're not trying to solve a problem that someone else has already figured out.


  1. Make sure your software does what the customer wants it to do.

    We should not be worrying about refactoring, designing, or applying patterns while we get to the first step. When we are still trying to reach a point of functionality, we don't know how the code will have to change, so prematurely over-designing the application is a recipe for cornering yourself.

  2. Apply basic OO principles to add flexibility.

    • Find mismatched objects. Objects should do what their names indicate. A Jet object should takeOff and land, but shouldn't taketicket, that's another object's responsibility.
    • Each object should represent a single concept. Avoid Duck objects that represent a quacking duck, a rubber duck, and someone dodging a baseball.
    • Unused properties are a dead giveaway. If an object is often used with no-value or null properties, you've probably got an object doing more than one job.
  3. Strive for a maintainable, reusable design.

    If a new requirement is requested and to add 1 thing we need to change it in multiple places, is there a way to improve the design so we don't need to update unrelated classes?

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