Java Performance Optimization Tips

While working on different Java apps, there arises the concept of optimization.

It is essential to maintain the cleanliness of the code, and it also doesn’t have any defects and is well optimized, that is, the execution time of the code should be within the intended time limit. For getting this, we have to refer to some primary Java coding standards.

Performance optimization is necessary for software app development with Java and different languages. With correct optimization techniques and an in-depth understanding of this language, one can improve the responsiveness and efficiency of different Java apps.

However, occasionally we do not have time to review the code because of deadline constraints. Here, we will discuss some tips that developers can keep in mind while performing coding in Java.

In this article, we will see different Java performance optimization tips such as memory management, data structure, concurrency, etc. So, let’s begin with the article.

What is Java Performance Optimization?

Java performance tuning or optimization is just a process to improve the performance of your Java app. There are different tips and tricks to improve your Java app.

Writing Java apps that perform well is tricky. Not only Java but other languages too.

There’s also a challenge of garbage collection in Java language. It’s like a two edge-sword but has also worked as a boon and curse.

Nevertheless, there are various best practices to follow which can help you develop a well-performing Java app. That’s what we’ll discuss in this post. Let’s discuss these techniques now.

Best Java Performance Optimization Tips and Techniques

Here are some techniques that you can ask your Java development company to provide you while developing your Java app.

Avoid Long methods

When you are writing methods in Java, make sure they are not too long. A method should always be unique for performing a single function.

It gets better to maintain small methods and improve performance while method call and class loading. Smaller methods load quickly in the memory stack and require less time.

If the methods are longer, too much processing time will be consumed and CPU cycles also execute more. If longer methods are created, try to break them into smaller methods as per the logic. Also, Java developer can strengthen their skills by knowing how to make function-specific methods that are easily executable.

Optimizing Memory Usage

Proper memory management can improve your Java app’s performance significantly. Here are some memory optimization tips to follow:

  • Try to use method parameters and local variables whenever possible, They have allotted places on the stack & have a smaller effect on memory management.
  • Use the method String.intern() for sharing instances of similar string literals, and minimizing memory footprint.
  • Try to minimize creating objects, especially in loops/code paths that are frequently executed. This technique will reduce garbage collection aloft.

Optimizing Loops

Loops in Java are the basic source of performance issues. So, keeping the loops optimized is something that can help developers with performance tuning in Java. Here are some tips for loop optimization:

  • Try to avoid method calling and calculations inside the loop by sending them outside the loop.
  • Apply the for-each loop, aka, enhanced for-loop when and where possible for better performance and readability.
  • Avoid developing objects in the loops as it can enhance garbage collection overhead.

Avoid using multiple if-else

Conditional statements are used for decision-making. However, overusing conditional statements is not appropriate. If there are many if-else conditional statements, the performance will be impacted as JVM has to compare all these conditions.

The situation can get worse if multiple for, while, etc., is used. Too many conditions in the business logic may be prone to create errors and impact smooth performance. So, developers should try to group these conditions and get simple boolean outcomes.

Also, using a switch statement can be a solution in such situations. Here’s one example of the code where multiple condition statements are used, and writing such codes should be avoided by developers:


if (condition_1) {

if (condition_2) {

     if (condition_3 || condition_4) { execute ..}

     else { execute..}

Kindly Note: The above example is to be ignored and here’s what one can use instead of the above code:

boolean result = (condition_1 && condition_2) && (condition_3  || condition_4)

Use the + operator for String concatenation in one statement

In the beginning, someone had probably told you that using + for string concatenation wasn’t a good idea in Java. This is correct if you are concatenating Strings in the app logic.

Strings in Java are immutable, and the solution of each concatenation is kept in a modern String object. Here, the string requires more memory and decreases the performance of your app. It happens especially when you are concatenating different strings in a loop.

In such cases, developers can use StringBuilder for easy String concatenation.

But it is not the case if you are breaking a String into different lines for improving the code readability.

For example:

Query a = em.createQuery(“SELECT, b.firstName, b.lastName” + “FROM Author c” + “WHERE = :id”);

In such a situation, you have to concatenate String with just a +. Your Java compiler will optimize and make concatenation at the time of compilation.

Try using Stored Procedures rather than Queries

It’s better to use Stored Procedures rather than long and complex queries and call them at the time of processing. Stored procedures are generally stored as objects inside the DB and pre-compiled.

The time of execution of the stored procedure is smaller as compared to queries that have the same business logic as queries that are compiled and executed every time whenever it is called using the app. Also, Stored Procedures have one advantage in network traffic and data transfer as we aren’t transferring complex queries every time for execution in the DB server.

Using ‘StringBuilder’ to concatenate Strings programmatically

There are various options available to concatenate Java Strings. You can use a simple += or + operator, StringBuffer or StringBuilder, for String concatenation.

So, the confusion is, which approach to use for Java String concatenation?

The solution depends on the code that helps with String concatenation. If one has to add new content programmatically to the String, such as for-loop then using StringBuilder is a good option.

StringBuilder provides better performance than StringBuffer and it is also easy to use. One has to keep in mind that these both are in contrast to each other and StringBuilder might not be a good alternative for all situations.

Developers just need an instantiation of a new StringBuilder and then make a call to the append method for adding a new part of the String. After you have added different parts, you can call the method toString() for retrieving the String that is concatenated.

Here’s a code snippet that showcases a simple example. During every iteration, the loop converts it into String and adds it with StringBuilder sb. So, the following code will give output somewhat like this:

“This is a test 0 1 2 3 4 5”

StringBuilder sb = new StringBuilder(“This is a test”);

for (int i=0; i<6; i++) {


sb.append(“ “);


As you see in the above example, you can give the first element of the String to the constructor method.

It will develop a new StringBuilder that contains the given String and has a capacity for sixteen more characters. As you add more characters to the StringBuilder, the JVM dynamically increases the size of that StringBuilder.

If you are aware of how many more characters you will add to the String, you can give that number to various constructor methods for instantiating the StringBuilder with a specific capacity.

This improves efficiency and does not need dynamic help for extending the capacity.

Select only Required Columns while writing a Query

While fetching the data from your database, you use a select query to fetch the data.

In this query, you should avoid selecting unnecessary columns for smoother processing. Use only those columns whose data is necessary for further processing.

If you are selecting unnecessary columns, it may cause a delay in executing the query at the end of the database. It also increases network traffic from DB to the app and causes performance glitches. 

Here’s a code snippet of a select query that should be avoided by developers:

Select * from employees where emp_id = 500;

The above query will return all the information of the employee whose ID is 500. Instead, if you have any specific requirement like you want to know the name, occupation, and address of that employee, here’s the query you can write:

select emp_name, emp_occupation, emp_address from employees where emp_id = 500;

Avoid using BigDecimal and BigInteger when not needed

When we talk about data types. We should take a glance at BigDecimal and BigInteger. BigDecimal is especially popular for its precision. But that comes with a price.

Both these data types need more memory than simple double or long data types and will slow down complex calculations dramatically.

So, developers should think twice before adding these data types to the code. They should only be used when the numbers might exceed a decided range of long data type and additional precision is required.

Try to avoid such data types when you need to fix the performance problem of your app, especially when you are using a mathematical algorithm.

Benchmark and Profile your code

For optimizing your Java app performance, you have to search for problem areas and bottlenecks. Use profiling tools like Java Flight Recorder, VisualVM, YourKit, etc., to monitor your app’s performance and search for areas that need improvement.

Moreover, you can use benchmarking tools like Java Microbenchmark Harness (JMH) for measuring the performance of unique code snippets and contrasting the influence of it on various optimization tips and techniques.

Use of caching and memoization

Memoization and caching help in optimizing the performance of the Java app by reusing and storing the solutions of expensive calculations. With the use of caching tips like Least Recently Used (LRU) memoization or cache for storing the results of intensive-resource operations and ignoring repeated calculations.

Keep Up-to-Date with Java Updates

Java language is a continuously evolving platform, and new updates in this language bring performance optimization and improvements. Keep the Java development and runtime environment updated for getting the proper advantages of new updates.

When you update to a new version, make sure to test your app rigorously, as a few updates might give compatibility issues or need coding updates.

Develop a performance test suite for a whole app

It is another general tip that helps you to circumvent lots of unexpected errors that can occur after you deploy your performance enhancement to production.

Developers should define a performance test suite testing the whole app, and execute it before performance improvement.

These additional test runs will help you search to identify the performance and functional side effects of your change and ensure that you do not publish an update that causes harm rather than doing good for the users.

Get the Collection size before the loop starts

One has to get the Collection size before the loop iteration starts and not while the iteration is going on. Here’s a simple example that illustrates the situation that a developer should avoid while writing Java code:

For example:

List<String> objList = getData ();

for (int a = 0; a < objList.size(); a++)

{line of code to be executed…}

This example has to be avoided. Here’s what developers can use instead of the above-mentioned code:

List<String> objList = getData();

int size = objList.size();

for (int a = 0; a < size; a++)

{line of code to be executed…}

Use primitive Data types whenever needed

The usage of primitive data types over the objects is advantageous as the primitive data is stored on a memory stack and the objects get stored in a heap.

If possible, developers can use primitive objects too as data is accessed from the stack which is faster than data access from heap memory. So, it’s always better to use int than Integer and double than Double.

Try to avoid creating big objects frequently

There are a few classes that work as data holders in the app. Such objects are big and their development should be avoided frequently.

For instance, such big objects are used in DB connection objects, system config objects, or session objects used after the login process. Such objects use multiple resources while they are created.

These objects should be reused instead of creating new objects every time. New object creation will drastically hamper the performance of the app because of hefty memory usage.

Developers can use the Singleton pattern when possible to develop a simple object instance and reuse it whenever and wherever needed. You can also clone such objects rather than make a whole new object.

Avoid the use of unnecessary Log Statements and Incorrect Log Levels

The logging part is an integral process of any app and requires it to be implemented properly for avoiding performance hits because of incorrect logging & logging levels. 

One should try to avoid big objects logging into the code. Logging has specific parameters and it should be limited to the same. Hence, we have to only monitor such parameters and not the whole object. 

Additionally, the logging level should have high levels like ERROR, not INFO, and DEBUG.

Here is a sample code that developers should avoid creating:

For example:

Logger.debug(“User Information : ” + user.toString());“Method called for setting user information:” + user.getData());


The above example is to be avoided. Here’s what developers can use instead of the above-mentioned code:

Logger.debug(“User Information : ” + user.getName() + ” : login ID : ” + user.getLoginId());“Method called for setting user information”);

Use Joins to fetch the data

While fetching the data from various tables, it is essential to use joins properly on these tables. However, if joins aren’t used properly, or the tables aren’t normalized it will make a delay in different query execution that leads to the performance hit on the app.

You should avoid using subqueries rather than joins because subqueries require more execution time than joins. Create one index on columns in the table that are used frequently. This process helps in improving the performance of query execution and reduces the application latency.

Cache costly resources such as DB connections

Caching provides a solution for avoiding the frequent execution of expensive code snippets.

The simple idea behind this is- Reusing expensive resources is cheaper than making a new resource again.

A typical instance is caching database connections in one pool. Creating a new connection each time will take more time, and it can be avoided by reusing the existing connection.

One can also search for other instances in the Java language itself. For instance, the valueOf() of the Integer class caches values from -128 to 127.

You might say that creation of some new integers is not too expensive, but it is used more frequently that the caching of most used values provides different performance advantages.

However, when caching is implemented, one should keep in mind that it will also create an overhead.

Additional memory is required to store the reusable resources that are cached. You also need to manage the cache for making the resources more accessible and remove outdated ones.

Hence, prior to you starting caching the resources, you need to ensure that you use the resources often to outweigh the cache implementation overhead.

Do not try to optimize until it is necessary

Optimization is one of the most essential performance tuning tips. By using some primary best practices, you should try to implement the use cases efficiently.

However, it does not mean that one should return any standard libraries and build strong optimizations prior to finding that it is necessary. 

In maximum cases, premature optimization takes a lot of time and makes the code hard for maintaining and reading it.

To make more worse, these optimizations most often do not provide any advantages as developers are spending a lot of optimization time on non-critical parts of the app.

So, how to know that optimization is needed now?

To begin with, you have to define how fast the app code should be, for instance, by specifying the maximum response time for API calls that have to be imported within a specific time frame.

After this, you can measure the parts of your app that are slow and need to be improved. And once this is done, you should start looking at other tips and techniques for Java performance optimization.

Develop a performance test suite for the whole app

It is another primary tip that helps you to overcome many unanticipated problems which often occur after you have deployed the performance improvements to the production.

You should define a whole performance test suite that helps in testing the whole app, and run it prior to and after you work on the optimization of the performance factor.

Additional test running will help developers to find the performance and functional side effects that change and ensure that you don’t publish an update that causes more harm than good.

It is important to work on optimizing the components which are used for many different parts of the app like caches and databases.

Select the right Data Structure

Picking the appropriate data structure for the use case is important for getting optimal performance. Java will provide a huge range of DS in the Collection Framework like LinkedList, ArrayList, TreeSet, and HashMap.

Understand their performance characteristics and pick the best one which suits your project requirements. For instance, if you often need deletions and insertions, you should use a LinkedList rather than an ArrayList.

Try to use Lazy Initialization

Using lazy initialization is a tip in which an object is used only when it is needed. This is used in circumstances where developing an object is quite expensive, and is not always required. Be careful while using this feature in multi-threaded environments, because you need to solve the synchronization problems.

Use PreparedStatement rather than Statement

While using the SQL query using the app we use JDBC API & classes for the same. PreparedStatement has special benefits over simple Statements for parameters containing query execution as the object of PreparedStatement is compiled and used whenever it is called. The prepared statement object is also safe for avoiding SQL injection that attacks the security of web apps.

Java Performance Optimization- Final Verdict

In the end, Java performance optimization is an essential pursuit for any developer thinking of creating a high-performing and robust Java app. 

By using the tips and techniques made in this article, developers can strongly enhance the speed and responsiveness of their Java code. Remember, the key lies in profiling the code, understanding the bottlenecks, employing appropriate DS and algorithms, leveraging parallelism and concurrency, and always keeping an eye on best practices. 

Quick monitoring and optimization are important to ensure that apps meet today’s performance demands and upgrade seamlessly in the face of future challenges. With a commitment to mastering these optimization strategies, Java developers can unlock the full potential of their code, delivering exceptional user experiences and staying at the forefront of the ever-evolving world of software development.


Rajib Is The Founder Of RiansTech. A Seasonal Blogger And A Full-Time Product Designer For Over Two Decades. A Technology Freak And Loves To Write About It. RiansTech Is A Online Home For Him Where He Documents His Experiences And Learnings So That Others Can Get Benefited From It.