22
Fri, Nov
1 New Articles

Java Journal: Refactoring

Java
Typography
  • Smaller Small Medium Big Bigger
  • Default Helvetica Segoe Georgia Times
My den meets all the criteria to be thought of as a software system. It takes input. The inputs are me and a bunch of reference material. It produces output. The output is a monthly Java column like the one you are reading right now. Seems like a pretty simple system with a well-defined interface of input and output. However, like most systems, it is far more complex than the interface would lead you to believe. Part of the reason for this complexity is that the system is doing something that it was not originally designed to do. In its infancy, my den was used for surfing the Web, watching TV, playing video games, and working on special projects. Later, it was primarily used for writing code for contract work and has slowly evolved into the column-writing system of the present. As my den passed through these various stages, it became somewhat less than tidy. There are stacks of books, piles of CDs, cables, and sticky notes galore. I remember purchasing a scanner a while back and even using it once or twice, so it must be under there somewhere. My den is exhibiting one of the fundamental laws of the universe. Specifically, my den is demonstrating the Second Law of Thermodynamics, which states that the universe tends toward a state of entropy. In the case of my den, I like to describe it as a "spontaneous increase in disorder." I've tried to explain this theory to my wife, but she insists that it won't harm the space-time continuum if I straighten up a little.

So it's time to clean the den, and I have a couple of ways I could go about it. One method would be to pull everything out of the bookshelves, file cabinets, and desk drawers, and then organize all my knickknacks and whatnots and, most importantly, throw things away that I don't need. I could unhook the computers and untangle the ball of wires that has accumulated behind the desk. This would be the right thing to do. There is only one problem with this method. From the time I begin cleaning until I have finished, I have disabled my Java column producing system. So there must be a better method. Another method would be to take an incremental approach, starting with something small like clearing off the desktop or organizing a drawer. This would allow me to improve the overall system without disabling it. Although the first method is probably preferable for getting everything done, the second method more closely resembles the way we have to make changes to software systems.

In his book Refactoring: Improving the Design of Existing Code, Martin Fowler describes refactoring as "the process of changing a software system in such a way that it does not alter the external behavior of the code yet improves its internal structure." So, in the case of my den, a refactoring could be any one of the small tasks mentioned above, because although they would improve the internal structure of my den, they would not affect the external behavior.

In software systems, you have probably already done refactoring from time to time. Usually, most people refactor when they are adding a new feature to a system and the current design is not flexible enough to accommodate it. So you refactor the design and then add a new feature. The result is that you get your new feature and improve your design. So if refactoring is a good thing to do, why do it only when you are forced to? Why not do it all the time? The most important goal when refactoring is to not alter the current behavior. Many people confuse refactoring with adding new functionality. Remember, you refactor first and then add the new functionality.

The only way to make sure that applying a refactoring has not changed the behavior of your system is to have good, automated tests. In Java, the best way to create automated tests is by using JUnit. For more information on JUnit, read my article on JUnit and automated testing. If you have good, automated testing, you can and should refactor all the time. Now, all you need to do is learn which refactorings are available to apply in a given situation and apply them.

There are several books on refactoring, but none even begins to compare to the original Refactoring by Martin Fowler mentioned above. Not only does he provide a great walkthrough example of how to apply refactorings, but he also provides a catalog of refactoring that he and his colleagues have come up with. Each refactoring in the catalog has a name, a summary, a motivation, the mechanics, and an example. Each of these properties is self-describing--except for possibly mechanics, which, simply put, are the steps that you would go through in order to apply a refactoring. Which brings up an interesting point. Any sort of task for which you can specify a series steps to complete can be automated and built into a tool such as your favorite Integrated Development Environment (IDE). In fact, both JBuilder and Together Control Center offer some minimal, automated refactoring support.

Some Refactoring Examples

The refactoring that I use the most is called Extract Method. In general, when I have a method that has grown too large or that I find myself cutting and pasting code out of, then I know that it is time to apply Extract Method. The goal of Extract Method is to remove a logical block of code from a method either to make the original method easier to understand or to make a block of logic available to be reused somewhere else. For my example, I'll use a method that prints a report by printing a header, a body, and then a footer. A stub for this method would look like the following:

  public void complicatedReportPrintingMethod()
  {
    /* Several lines of code that print the report header
       ...
    */

    /* A bunch of code that prints the report body
       ...
    */

    /* Several lines of code that print the report footer
       ...
    */
  }


Rather than bog you down in a lot of code that you don't care about, I will just assume that each of the comment blocks is a significant number of lines of code.

Now, for the purposes of this example, let's say that you have a requirement to add a new report to your system that has the same header and footer as your current report. You will want to extract the code for the header and footer into their own methods by applying the Extract Method refactoring twice. However, before doing any refactoring, make sure that you have good test coverage for the code that you are about to change. If needed, add some new tests. Then, run all the tests to make sure that they all pass. Only then should you apply the Extract Method refactoring twice, once to the header block of code and once to the footer block of code. The resulting code would look like the following:

  public void complicatedReportPrintingMethod()
  {
    this.printHeader();

    /* A bunch of code that prints the report body
       ...
    */

    this.printFooter();
  }

  public void printHeader()
  {
    /* Several lines of code that print the report header
       ...
    */
  }

  public void printFooter()
  {
    /* Several lines of code that print the report footer
       ...
    */
  }


Once the refactoring is done and you have verified that the automated tests all still pass, you could add the new report, which you would call printHeader() and printFooter(). (Note: There are a lot of rules for how to extract a method that I am skipping over here for the sake of simplicity.) So now, suppose you decide that you want to add yet another report and your class is getting lots of independent methods in it. You might make an abstract base class for the reports and then have each report inherit from this new base class. When doing this, you will want to move printHeader() and printFooter() to this new abstract base class by applying a refactoring called Pull Up Method. As I mentioned earlier, some IDEs are now incorporating tools to help you do refactoring automatically. So, to do the Extract Method in the above example, all you would have to do is highlight the code that you wish to extract, select the appropriate refactoring, and then name the new method.

Some Other Benefits

There are several other benefits to refactoring. First, some refactorings tie in tightly with design patterns. Design patterns are a proven way to reuse design. For more information on design patterns and design reuse, see my article on design patterns. An example of such a refactoring would be Replace Type Code with State/Strategy. The state and strategy design patterns really let you leverage the power of your objects by decoupling interfaces from implementations. Second, you will find that as you learn more and more of the refactoring techniques, you will write better code to begin with because you will produce the equivalent of already refactored code on the first pass. This is not to say that you won't want to still refactor more; there is always room for improvement, and in almost any significant piece of code, you will find many opportunities to refactor. Third, most refactoring techniques work in multiple languages, and while many are based on the premise that your language is object-oriented, many more are not and are applicable to sequential and object-oriented languages alike.

Where to Get More Information

In addition to the Refactoring book, there is a refactoring Web site where you can find up-to-date information and discussion of all the latest tools and techniques. I list only this one site because it is both updated frequently and contains links to all the refactoring information in the known universe.

Recap

Refactoring is about changing the internal design of code without changing its external behavior. Don't confuse refactoring with adding functionality--refactor first, then add functionality. Learn to continuously refactor and add new automated tests if you are unsure of the test coverage of the code you are refactoring. Start by learning simple, common refactorings like Extract Method, and then build your confidence and branch out to others. Some refactorings like Replace Type Code with State/Strategy are particularly effective, and they allow you to incorporate proven design patterns into your system. Once you become confident with refactoring techniques, you will find that you write better code to begin with. Although some refactorings are geared toward object-oriented languages, there are many that can be used in sequential languages. Refactoring is how we fight the Second Law of Thermodynamics and keep our systems from becoming chaotic, so I think I will start with the bookshelves before it's too late.

Michael J. Floyd is an Extreme Programmer and the Software Engineering Technical Lead for DivXNetworks. He is also a consultant for San Diego State University and can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..

Michael Floyd

Michael J. Floyd is the Vice President of Engineering for DivX, Inc.

BLOG COMMENTS POWERED BY DISQUS

LATEST COMMENTS

Support MC Press Online

$

Book Reviews

Resource Center

  • SB Profound WC 5536 Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application. You can find Part 1 here. In Part 2 of our free Node.js Webinar Series, Brian May teaches you the different tooling options available for writing code, debugging, and using Git for version control. Brian will briefly discuss the different tools available, and demonstrate his preferred setup for Node development on IBM i or any platform. Attend this webinar to learn:

  • SB Profound WP 5539More than ever, there is a demand for IT to deliver innovation. Your IBM i has been an essential part of your business operations for years. However, your organization may struggle to maintain the current system and implement new projects. The thousands of customers we've worked with and surveyed state that expectations regarding the digital footprint and vision of the company are not aligned with the current IT environment.

  • SB HelpSystems ROBOT Generic IBM announced the E1080 servers using the latest Power10 processor in September 2021. The most powerful processor from IBM to date, Power10 is designed to handle the demands of doing business in today’s high-tech atmosphere, including running cloud applications, supporting big data, and managing AI workloads. But what does Power10 mean for your data center? In this recorded webinar, IBMers Dan Sundt and Dylan Boday join IBM Power Champion Tom Huntington for a discussion on why Power10 technology is the right strategic investment if you run IBM i, AIX, or Linux. In this action-packed hour, Tom will share trends from the IBM i and AIX user communities while Dan and Dylan dive into the tech specs for key hardware, including:

  • Magic MarkTRY the one package that solves all your document design and printing challenges on all your platforms. Produce bar code labels, electronic forms, ad hoc reports, and RFID tags – without programming! MarkMagic is the only document design and print solution that combines report writing, WYSIWYG label and forms design, and conditional printing in one integrated product. Make sure your data survives when catastrophe hits. Request your trial now!  Request Now.

  • SB HelpSystems ROBOT GenericForms of ransomware has been around for over 30 years, and with more and more organizations suffering attacks each year, it continues to endure. What has made ransomware such a durable threat and what is the best way to combat it? In order to prevent ransomware, organizations must first understand how it works.

  • SB HelpSystems ROBOT GenericIT security is a top priority for businesses around the world, but most IBM i pros don’t know where to begin—and most cybersecurity experts don’t know IBM i. In this session, Robin Tatam explores the business impact of lax IBM i security, the top vulnerabilities putting IBM i at risk, and the steps you can take to protect your organization. If you’re looking to avoid unexpected downtime or corrupted data, you don’t want to miss this session.

  • SB HelpSystems ROBOT GenericCan you trust all of your users all of the time? A typical end user receives 16 malicious emails each month, but only 17 percent of these phishing campaigns are reported to IT. Once an attack is underway, most organizations won’t discover the breach until six months later. A staggering amount of damage can occur in that time. Despite these risks, 93 percent of organizations are leaving their IBM i systems vulnerable to cybercrime. In this on-demand webinar, IBM i security experts Robin Tatam and Sandi Moore will reveal:

  • FORTRA Disaster protection is vital to every business. Yet, it often consists of patched together procedures that are prone to error. From automatic backups to data encryption to media management, Robot automates the routine (yet often complex) tasks of iSeries backup and recovery, saving you time and money and making the process safer and more reliable. Automate your backups with the Robot Backup and Recovery Solution. Key features include:

  • FORTRAManaging messages on your IBM i can be more than a full-time job if you have to do it manually. Messages need a response and resources must be monitored—often over multiple systems and across platforms. How can you be sure you won’t miss important system events? Automate your message center with the Robot Message Management Solution. Key features include:

  • FORTRAThe thought of printing, distributing, and storing iSeries reports manually may reduce you to tears. Paper and labor costs associated with report generation can spiral out of control. Mountains of paper threaten to swamp your files. Robot automates report bursting, distribution, bundling, and archiving, and offers secure, selective online report viewing. Manage your reports with the Robot Report Management Solution. Key features include:

  • FORTRAFor over 30 years, Robot has been a leader in systems management for IBM i. With batch job creation and scheduling at its core, the Robot Job Scheduling Solution reduces the opportunity for human error and helps you maintain service levels, automating even the biggest, most complex runbooks. Manage your job schedule with the Robot Job Scheduling Solution. Key features include:

  • LANSA Business users want new applications now. Market and regulatory pressures require faster application updates and delivery into production. Your IBM i developers may be approaching retirement, and you see no sure way to fill their positions with experienced developers. In addition, you may be caught between maintaining your existing applications and the uncertainty of moving to something new.

  • LANSAWhen it comes to creating your business applications, there are hundreds of coding platforms and programming languages to choose from. These options range from very complex traditional programming languages to Low-Code platforms where sometimes no traditional coding experience is needed. Download our whitepaper, The Power of Writing Code in a Low-Code Solution, and:

  • LANSASupply Chain is becoming increasingly complex and unpredictable. From raw materials for manufacturing to food supply chains, the journey from source to production to delivery to consumers is marred with inefficiencies, manual processes, shortages, recalls, counterfeits, and scandals. In this webinar, we discuss how:

  • The MC Resource Centers bring you the widest selection of white papers, trial software, and on-demand webcasts for you to choose from. >> Review the list of White Papers, Trial Software or On-Demand Webcast at the MC Press Resource Center. >> Add the items to yru Cart and complet he checkout process and submit

  • Profound Logic Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application.

  • SB Profound WC 5536Join us for this hour-long webcast that will explore:

  • Fortra IT managers hoping to find new IBM i talent are discovering that the pool of experienced RPG programmers and operators or administrators with intimate knowledge of the operating system and the applications that run on it is small. This begs the question: How will you manage the platform that supports such a big part of your business? This guide offers strategies and software suggestions to help you plan IT staffing and resources and smooth the transition after your AS/400 talent retires. Read on to learn: