24 Ways To Improve Your Java Performance

When using Java to develop your sites and apps, you want to write code that isn’t just serviceable and easy and pleasurable to use. After all, you want your users to keep coming back for more, again and again. With these tweaks to your programming style, you’ll be able to get the most out of Java every time.

Getting the Best Performance from Java

Great applications in Java are usually those that are as fast and useful as possible. Today, most users expect their apps to work quickly and will not hang around if their current providers fail to perform to par.
When it comes to performance, two main things can cause problems: lousy design or code issues. As you’ll see in this guide, many factors are influencing the app code. To avoid these issues, you’re going to make coding a lot simpler.
In coding, a helpful mental note to keep is knowing you will make errors in the process. No one makes things perfectly the first time, and experienced programmers know that mistakes constantly sneak through. Java is more intuitive than most languages, but there is still a gap between humans and computers. You won’t always get it right, and that’s why you need to know what factors are in play when it comes to code consistency.

Actions You Can Take To Improve Java Performance

There are a few proven methods you can use to improve the performance of your code before you get into the specifics. Here’s what you can do as you’re coding to keep errors to a minimum and improve that performance.

Perform profiling and load testing: Performing regular tests will quickly reveal any bottlenecks so that you can address issues quickly.

Avoid recursion: While sometimes you can’t avoid recursion, you should try and avoid it wherever you can.

Upgrade hardware and bandwidth: If you’re experiencing problems, the issue may not be in the code but your hardware or LAN or WAN bandwidth. Address these issues so that you can rule them out.

Clean up code and algorithms: The cleaner your code is, the easier it is to maintain. Keep it as clean as possible so you can stay on top of any issues and provide an easier ground for collaboration.

24 Ways To Improve Java Performance

  1. Use Constructor For Instantiating 
    If your collections initialize only once, it’s better to send them to the Constructor collection. This method works better than instantiating the collections and setting values with AddAll.
  2. Use AddAll Rather Than Add
    If you’re adding something to an array, then it’s better to use AddAll, rather than Add. AddAll offers you higher operations per second.
  3. Use EntrySet Rather Than KeySet
    Similarly, changing up command will help you get a much faster and smoother experience. If you are iterating a lot over the map, then EntrySet will work better than KeySet. EntrySet can run 9000 more operations than KeySet in a single second, so you’re going to get much better performance this way.
  4. Try SingletonList Instead Of Single Element Array 
    If you need to return a list with just the specified index, use SingletonList to do so. As the name implies, the list here will only contain the specified object. The returned list is serializable and will help you improve the usability of your code.
  5. EnumSet Is the Best Option for Enum Value 
    If you are working with Enum values, it makes a lot more sense to work with EnumSet. It allows for faster computations than other methods, making the finished product faster overall. The values of EmunSet are stored in a predictable order, whereas other methods, like HashSet, takes longer to produce the same results.
  6. Do not Initialize Objects at Will
    When working with Java, it is always better to try and look at the bigger picture before threading on a single channel of code build-up. For example, you can try and initialize objects as you go along creating code, but this can result in unnecessary chunks of workload, which, piled up in time, will soon reach mind-blowing proportions. Try to reuse at the maximum. That way, you get two substantial benefits right away: 1) your job is more manageable, and 2) your code is cleaner.
  7. Use The Right Commands To Check Strings
    Need to know if a string is empty? Then the best command is String.isEmpty(). This function works because String is a byte[] and isEmpty checks the array’s length. That way, you can get results much faster when checking.
  8. Replace Single Character Strings With A Character
    Adding a singular character in these strings makes things much faster overall, so you are speeding up the coding process again.
  9. Make Sure You are Using StringBuilder 
    is another tool for strings that are done easier in Java. While many would use StringBuffer, it is not as quick to use as StringBuilder. To check for yourself, instantiate a new StringBuilder and call the append method to add new parts to the string. Once all the working parts are in place, you can use the toString() command and retrieve the string itself. Be aware that StringBuilder is not thread-safe, and so it may not work in all cases for you.
  10. Use Primitives Wherever Possible
    ‘Primitive types are a suitable alternative to wrapper classes,’ says tech writer Nikola Heath, from 1 Day 2 Write and Write My X. ‘They help reduce memory consumption, and so increase efficiency.’ In these cases, it is better to use an int instead of Integer and double for Double. Using these wherever you can help improve overall performance.
  11. Always Work On The Biggest Problem First
    After creating the test suite and moving to problem-solving, there will always be several unaddressed issues. You can hunt the minor problems first because they are quick to fix. However, it is better to work on the most significant issue before anything else.
    When you tackle the more complex items right away, your performance will increase, and you may be able to get the code approved quicker without having to handle the more minor issues.
  12. + Can Be Used To Concatenate Your Strings In One Statement
    When learning Java, you may have remembered that you should not use ‘+’ to concatenate strings. That is true if you are doing so in your application logic. However, you can do so if you break your String into multiple lines to make it more readable. In these cases, you can do so with a simple ‘+.’
  13. Use Apache Commons StringUtils.replace
    Most coders will use String.replace, and that will work perfectly for their needs. There are faster ways you can do this for those who need a lot of replacement operations. Apache Commons StringUtils.replace works perfectly if you are using Java 8, and it is a lot faster than the native option. If you are on the latest version of Java, though, you may be better off with String.replace.
  14. Avoid BigInteger And BigDecimal
    Programmers use these data types a lot as they offer a lot of precision. The problem is, though, they use a lot of memory, which affects the total production speed of the end product. While sometimes you cannot avoid them, it is best not to use them at all if possible. Long or double commands often give you what you need, which may be enough to improve performance in your code.
  15. Always Check the Log Level
    When creating any log within your code, you need to ensure that your logging framework will support the log message. If you do not, you may make a message that the code ignores and remain invisible. Just doing this will save work later.
  16. Make Sure You are Using Caching
    You will know that reusing code snippets is much cheaper than creating new ones every time you need them. That is why you must use caching when using Java. Some instances of caching are built into the language itself. For example, the valueOf method caches the values between -128 and 127.
    When using caching, you will need to remember that it does still require some memory. You will need to create a balance, using caching to make sense and untapped resources where needed.
  17. Do not Optimize Before You Need To
    It seems like it makes sense to start optimizing as soon as possible, but the opposite is true. ‘If you start optimizing too early, you could make the code harder to maintain,’ says writer Patrick Slater at Brit Student and Next Coursework. ‘You’ll usually need to make more changes down the line, and so it’ll take longer to deal with overall.’
    If you feel you need to optimize something right away, compare it to your original plan. How fast does your code need to execute, and how much is this section slowing down? If it’s a significant decrease, then it is safe to work on it.
  18. Run Performance Test Suites After Improvements
    To get code that is running as you want it to, you must test after making improvements. Define a performance test suite that examines the whole application you are coding, and run it before and after changes.
    Such a test gives you the hard data on what is and is not helping your code. It also ensures you are shipping the best product possible, so make sure you run those tests, and make them part of your developmental routine.
  19. Keep Methods Short
    When creating any methods in your code, it is best to keep them as short as possible. Usually, any method should work on a single functionality – it improves overall performance and makes things easier for you when it comes to maintenance. More extensive ways will use more memory and slow everything down. It is better to have your methods broken down into smaller ones.
  20. Do not Get the Size Of The Collection In The Loop
    If you are iterating any collection, please plan for its size beforehand and not in the iteration itself. Not accomodating for collection size is another common mistake that slows down code and makes things harder for you when programming.
  21. Avoid Creating Big Objects When Possible
    In coding, certain classes will act as data holders. They will take up memory, so it is always better to avoid creating them whenever possible. DB connection objects, system configuration objects, and session objects are all excellent examples of these.
    While creating, they use many resources, so it is better to reuse these wherever you can in the code.
  22. Try PreparedStarement Instead Of Statement
    When executing an SQL query through your application, PreparedStatement will usually be better for performance than Statement. The PreparedStatement object is compiled once and is run multiple times, unlike Statements, collected every time upon use.
  23. Ensure You are Using Joins Properly
    When fetching data from multiple tables, joins are needed. If you failed to implement them correctly, more delays in order execution might appear. That results in performance issues, which are otherwise easily avoidable. Creating an index of table columns that are frequently in use can help improve performance speeds.
  24. Avoid Unnecessary Logging
    In point 15, you saw how you need to check the log level before logging anything. All logging needs to be efficient so that it will not affect performance speeds. Usually, the best way to do this is to log only within specific parameters and avoid placing big objects into the log.

Use this guide to accommodate for all the different things that can be affecting your Java performance and code. Make the necessary adjustments, and see how much of a difference it makes.  
If you enjoyed this article, please check a few of our other articles about tips and tricks for programmers.


David Dorr, Head of eCommerce

David is the Head of e-Commerce at CodeCoda where he is responsible to lead several teams of eCommerce specialists. In his previous role as a data scientist for London Metropolitan Police, he was developing deep learning NLP algorithms as part of the Crime Prediction initiative. He then switched over to combine AI with e-Commerce.
He received a B.Sc in Physics from the University of Surrey, Guildford in 1996. With this scientific background, he switched relatively early in his life towards Neural Networks and e-Commerce and has ever since been fascinated with what AI and Machine Learning can do for Online Commerce.