Head First Design Patterns: A Brain-Friendly Guide

Author: Eric Freeman, Elisabeth Freeman, Kathy Sierra, Bert Bates
All Stack Overflow 99
This Year Stack Overflow 4
This Month Stack Overflow 1


by zerogvt   2019-01-20
Head first is a much better option IMO https://www.amazon.com/Head-First-Design-Patterns-Brain-Frie...
by IllusionsMichael   2019-01-13


by ZukoBestGirl   2019-01-13




And you could check stack overflow for question on general programming books. I would always go for a general concept functional programming over how to functional programming in haskell.

But I'll be perfectly honest, I'm a victim of the curse of knowledge so I honestly don't know how one should start. What I do remember is that I had huge problems with syntax (how do I tell language X to do a for (Employee e in employeeList), how do you write a switch and stuff, why would I ever need a ternary operator, and like that.

But once you master the basics of how to write x, y and z in your preferred language, you absolutely need to understand design patterns, you absolutely need to understand how code is supposed to be written, you absolutely need to understand data structures, you absolutely need to understand inheritance and polymorphism, you absolutely need to understand lambdas and functional programming.

Then you can get to the more "neat" stuff like the benefits of having immutables, and "job specific stuff" like how to solve race conditions in threading; sockets and web communication, etc.

by thorin   2018-09-28
I used to like Thinking in Java [1], but not sure how it holds up now, I think I read the first the edition.

I enjoyed reading the headfirst patterns book as a refresher

[1] https://sophia.javeriana.edu.co/~cbustaca/docencia/POO-2016-... [2] https://www.amazon.com/Head-First-Design-Patterns-Brain-Frie...

by user295190   2018-03-19

Hope this helps. It describes the various types of factories. I used Head First Design Patterns as my reference. I used yuml.me to diagram.

Static Factory

Is a class with a Static Method to product various sub types of Product.

Static Factory

Simple Factory

Is a class that can produce various sub types of Product. (It is better than the Static Factory. When new types are added the base Product class does not need to be changed only the Simple Factory Class)

Simple Factoryt

Factory Method

Contains one method to produce one type of product related to its type. (It is better than a Simple Factory because the type is deferred to a sub-class.)

Factory Method

Abstract Factory

Produces a Family of Types that are related. It is noticeably different than a Factory Method as it has more than one method of types it produces. (This is complicated refer to next diagram for better real-life example).

Abstract Factory

Example From The .NET Framework

DbFactoriesProvider is a Simple Factory as it has no sub-types. The DbFactoryProvider is an abstract factory as it can create various related database objects such as connection and command objects.

Abstract Factory From .NET Framework ​​​

by anonymous   2018-03-19

I've taken a class in college that spent two weeks around design patters, and read the Gang of Four book to no avail. Understanding what each pattern served for and how to use them to fit my problems was very hard for me, a developer that didn't have much experience in OO programming.

The book that really made it click for me was Head First Design Patterns. It starts by showing a problem, different approaches the developers considered, and then how they ended up using a design pattern in order to fix it. It uses a very simple language and keeps the book very engaging.

Design patterns end up being a way to describe a solution, but you don't have to adapt your classes to the solution. Think of them more as a guide that suggest a good solution to a wide array of problems.

Let's talk about SOLID:

  1. Single responsibility. A class should have only one responsibility. That means that for example, a Person class should only worry about the domain problem regarding the person itself, and not for example, its persistence in the database. For that, you may want to use a PersonDAO for example. A Person class may want to keep its responsibilities the shortest it can. If a class is using too many external dependencies (that is, other classes), that's a symptom that the class is having too many responsibilities. This problem often comes when developers try to model the real world using objects and take it too far. Loosely coupled applications often are not very easy to navigate and do not exactly model how the real world works.
  2. Open Closed. Classes should be extendible, but not modifiable. That means that adding a new field to a class is fine, but changing existing things are not. Other components on the program may depend on said field.
  3. Liskov substitution. A class that expects an object of type animal should work if a subclass dog and a subclass cat are passed. That means that Animal should NOT have a method called bark for example, since subclasses of type cat won't be able to bark. Classes that use the Animal class, also shouldn't depend on methods that belong to a class Dog. Don't do things like "If this animal is a dog, then (casts animal to dog) bark. If animal is a cat then (casts animal to cat) meow".
  4. Interface segregation principle. Keep your interfaces the smallest you can. A teacher that also is a student should implement both the IStudent and ITeacher interfaces, instead of a single big interface called IStudentAndTeacher.
  5. Dependency inversion principle. Objects should not instantiate their dependencies, but they should be passed to them. For example, a Car that has an Engine object inside should not do engine = new DieselEngine(), but rather said engine should be passed to it on the constructor. This way the car class will not be coupled to the DieselEngine class.
by anonymous   2018-03-19

A book I'd highly recommend to you for MVC in swing would be "Head First Design Patterns" by Freeman and Freeman. They have a highly comprehensive explanation of MVC.

Brief Summary

  1. You're the user--you interact with the view. The view is your window to the model. When you do something to the view (like click the Play button) then the view tells the controller what you did. It's the controller's job to handle that.

  2. The controller asks the model to change its state. The controller takes your actions and interprets them. If you click on a button, it's the controller's job to figure out what that means and how the model should be manipulated based on that action.

  3. The controller may also ask the view to change. When the controller receives an action from the view, it may need to tell the view to change as a result. For example, the controller could enable or disable certain buttons or menu items in the interface.

  4. The model notifies the view when its state has changed. When something changes in the model, based either on some action you took (like clicking a button) or some other internal change (like the next song in the playlist has started), the model notifies the view that its state has changed.

  5. The view asks the model for state. The view gets the state it displays directly from the model. For instance, when the model notifies the view that a new song has started playing, the view requests the song name from the model and displays it. The view might also ask the model for state as the result of the controller requesting some change in the view.

enter image description here Source (In case you're wondering what a "creamy controller" is, think of an Oreo cookie, with the controller being the creamy center, the view being the top biscuit and the model being the bottom biscuit.)

Um, in case you're interested, you could download a fairly entertaining song about the MVC pattern from here!

One issue you may face with Swing programming involves amalgamating the SwingWorker and EventDispatch thread with the MVC pattern. Depending on your program, your view or controller might have to extend the SwingWorker and override the doInBackground() method where resource intensive logic is placed. This can be easily fused with the typical MVC pattern, and is typical of Swing applications.

EDIT #1:

Additionally, it is important to consider MVC as a sort of composite of various patterns. For example, your model could be implemented using the Observer pattern (requiring the View to be registered as an observer to the model) while your controller might use the Strategy pattern.

EDIT #2:

I would additionally like to answer specifically your question. You should display your table buttons, etc in the View, which would obviously implement an ActionListener. In your actionPerformed() method, you detect the event and send it to a related method in the controller (remember- the view holds a reference to the controller). So when a button is clicked, the event is detected by the view, sent to the controller's method, the controller might directly ask the view to disable the button or something. Next, the controller will interact with and modify the model (which will mostly have getter and setter methods, and some other ones to register and notify observers and so on). As soon as the model is modified, it will call an update on registered observers (this will be the view in your case). Hence, the view will now update itself.

by anonymous   2017-08-20

You have to make up your mind whether the so called apple-specific method (in this case checkPrice()) is really specific to Apple. Or it is actually generally applicable to all fruits.

A method that is generally applicable should be declared in the base class

Assuming the answer is yes (in this case it does seems to be yes), then you should declare the method in the base class. In this case you can iterate through all the different types of fruits, and all of them would accept the method checkPrice(), so you don't even need to make a special case for apples.

A method that isn't generally applicable can be declared in an interface

What if the answer is no? Let's assume we need another method called getJuicePrice(), and we further assume that only some fruits can be made into juice (apple juice, orange juice) but other cannot (pineapple? durian?). In this case, a simple solution is to declare an interface, and only the fruits for which the method is appropriate would implement the interface. So let's say this interface is JuiceBehavior

package fruitcart;

import java.math.BigDecimal;

public interface JuiceBehavior {
    BigDecimal getJuicePrice();

And all fruits for which juice behavior is applicable (yes for Apple, no for Durian) would implement the interface:

package fruitcart;

import java.math.BigDecimal;

public class Apple implements JuiceBehavior {

    public BigDecimal getJuicePrice() {
        // FIXME implement this
        return null;


And then in your loop, what you check is whether a fruit is instanceof the interface:

if (fruit instanceof JuiceBehavior) {
    System.out.format("can be made into juice "
        + "with price $ %.2f%n", fruit.getJuicePrice());
} else {
    System.out.format("cannot be made into juice %n");


This solution would work for simple cases, but in more complicated cases, you may notice that you start to duplicate a lot of implementation code for getJuicePrice() for different types of fruits. This leads to the next topic

Design Pattern: Strategy

You may want to start thinking about the Design Pattern called Strategy, which further encapsulates JuiceBehavior and make it into a family of classes representing different juice behaviors. It also let you set different types of fruits to take different implementations of JuiceBehavior. I won't go into the details here. But you can read up on that on some books about Design Patterns. Such as

  1. Design Patterns: Elements of Reusable Object-Oriented Software
  2. Head First Design Patterns: A Brain-Friendly Guide
by anonymous   2017-08-20

The Decorator Pattern is probably the most straight forward one to use and would be a good one to extend concrete objects functionality and/or characteristics.

Here is some light reading: Head First Design Patterns - CH3 pdf

FYI, couple must have's for learning and referencing design patterns regardless your language of choice:

1) Head First Design Patterns

2) Patterns for Enterprise Application Architecture

3) Design Patterns: Elements of Reusable Object-Oriented Software

And sites:

1) DoFactory

2) StackOverflow Design Patterns Newbie

There are a few others, I'll have to dig them up.