Programming Corner

I have been reading about Design Pattern lately, and I ran across some articles about the Builder Pattern that are not accurate at all. Because of that, I decided to write a short article about what this pattern is and how to properly implement it. I will start by providing a short description of what this pattern is. I will follow that with some context by providing hypothetical usages for this pattern, and conclude with a (hopefully good) code example. What is the Builder Pattern? Even these bad articles got one thing right: The Builder Pattern is a Creational Pattern . This means that the pattern's main goal is to provide a reusable solution for creating objects. You may ask, why are there more than one creational pattern? Isn't invoking a class constructor enough? Well... yes and no. Why use Builder Pattern? Experts (people who know more than me) have determined that using one of these creational patterns is preferred over invoking the constructor of a c

On previous articles, I wrote about real-world usages for the State and Singleton design patterns. I also wrote about using these two patterns together to create a state-machine. Now, I am going use that state-machine to control a Wizard. I am going to use Java Swing to create the User Interface classes. To create my interface using Java Swing, I am going to create three panels for contents, one panel to provide the navigation controls, and a frame to hold it all together. It will be a simple example, but one you could easily expand should you have the need to create your own wizard. The Frame The frame is the application window. I will not go to much into details about the Java JFrame class, as I assume you have some basic knowledge of Java and Java Swing. If you don't much about Java Swing, I suggest you visit this Oracle tutorial on how to create frames . Main.java public class Main extends JFrame { private CardsPanel cards = new CardsPanel(); private Navi

In my previous two posts, I discussed real-world applications for the Singleton and State design patterns. In this article, I am going to illustrate how to combine both of these patterns to create a simple wizard. Simple State Design Pattern Implementation In a typical implementation of the design pattern, State is either an interface or abstract class, with each state of the state machine being Singleton classes. My example is going to be slightly different. I will implement the state machine using a state interface and Java enums to implement the Singleton. Using an enum is the recommended way to implement a Singleton in Java. First, let's come up with a simple state interface State.java public interface State { void goNext(Context input); void goPrevious(Context input); } Now that we have an interface defined, we can derive as many states as we need. For this example, three states should be sufficient to demonstrate the wizard's functionality. Jav

I believe this is the most important aspect of Object-Oriented Design (OOD) and Programming (OOP). I also believe this is the most disregarded. It is disregarded because it is not fully understood. It is my opinion that this aspect of OOP is misunderstood because beginner programmers focus in learning WHAT encapsulation is, and not why it is important or needed. This article aims to explain why encapsulation is important and how to achieve true encapsulation. Although anyone could look up its definition in a dictionary, I would like to start by defining the word 'encapsulation.' Encapsulation simply means to enclose something in. To completely cover or hide something especially so that it will not touch (or come in contact with) anything else. In the real world, there are many reasons to encapsulate. For example, certain medication come in the form of capsules. The real value of medicinal capsules in in the medicine that it encloses. To make a long story short, med

Introduction to Exception Handling This is a supplement to my previous blog Creating Custom Exception Classes in Java . I recommend you read that one first and then read this one. Java provides many Exception (and Error) Handling classes. Both of these categories implement the Throwable interface. Although it is not imperative that you develop your own custom exception classes, it is often a good idea to do so; particularly when dealing with large systems. The main reason to create custom exception classes is to quickly identify which custom class is being affected or causing these custom exceptions. For example, referencing a null object and trying to use it will result in a NullPointerException . However, in your code, there could be literally hundreds or even thousands of statements which could result in such exception. Designing your Custom Exception Class Suppose that you are designing a class that will serve as a message receiver. For simplicity,

Introduction My first piece of advice: Search the web. There is a ton of information that is available to you on the Internet. However, beware where you go for information. There are many places with bad information as well. For this topic, the safest source of information is the Oracle The Java Exceptions Tutorials . Starting with the basics, the first thing to do is determine whether or not you need the custom exception class to begin with. We are going to assume we need to handle an exception that it is not clearly represented already in Java. To create a custom exception class, we must use a name that it is meaningful. Typically, the exception class is named after a process or a class name that will throw the exception. For instance, if I create a MessageReceiver class that could result in an exception, I might consider naming my exception class MessageReceiverException. The UML diagram below depicts this relationship between the class and the custom

This document is a summary of the information found on the Oracle website: http://www.oracle.com/technetwork/java/javase/documentation/index-jsp-135444.html My goal is to give you a summarized version of the following topics: ·          What is Javadoc and why is it needed? ·          How to document your code using Javadoc ·          How to generate Javadoc documentation ·          How to publish Javadoc What is Javadoc and why is it needed? In simple terms, Javadoc is a tool for documenting your code in HTML format. Because this documentation is in HTML, it can be easily uploaded to a web server and made available online for the whole world to see. An example of this is the Java API ( https://docs.oracle.com/javase/8/docs/api/ ). For many developers, one of the selling points of Java over other languages like C++ was in fact Javadoc. Why? If you consider one of the most common libraries in C++, stdio, most of the documentation found online is