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Understanding Java Performance and 8 Performance Tuning Tips 

Ofer Dekel

Product Manager, Intel Granulate

What Is Java Performance? 

Java performance refers to the speed and efficiency of a Java application or system, and is typically measured by the amount of time it takes to complete a particular task or the amount of resources it uses to do so. Performance is a critical factor in many applications, particularly those that require real-time processing, high throughput, or low latency.

In Java, performance can be affected by a variety of factors, including the code itself, the JVM implementation, and the hardware it runs on. Common performance bottlenecks include inefficient algorithms, excessive memory usage, excessive CPU usage, and I/O operations. These issues can often be identified and addressed through profiling, tuning, and optimization.

This is part of an extensive series of guides about performance testing.

In this article:

5 Common Java Performance Problems 

1. Memory Leaks and Out of Memory Errors

A memory leak occurs when a program continues to allocate memory without releasing it, causing memory usage to increase over time. This can lead to an OutOfMemoryError, which is a runtime error that occurs when the Java virtual machine (JVM) runs out of memory. The JVM has a maximum heap size that can be allocated for objects in memory, and once this limit is reached, it throws the OutOfMemoryError.

2. Thread Deadlocks

A thread deadlock is a situation that occurs in multithreaded programming when two or more threads are waiting for each other to release a resource, such as a lock or database connection, causing the application to freeze or hang. In other words, a deadlock occurs when two or more threads are blocked indefinitely, waiting for each other to release the resources they need to proceed.

Thread deadlocks can be difficult to identify and fix because they often involve complex interactions between different threads, and they may not be immediately obvious. However, they can be a serious problem in a multithreaded application, as they can cause the application to become unresponsive and eventually crash.

3. Garbage Collection

In Java, a garbage collector is a mechanism that automatically frees up memory by deleting objects that are no longer being used by the application. The garbage collector runs periodically in the background and identifies objects that are no longer being referenced by the application. It then frees up the memory occupied by those objects, making it available for future use.

When the garbage collector is full, the JVM may attempt to free up memory by running the garbage collector more frequently or by using different garbage collection algorithms. However, if the memory usage continues to exceed the maximum heap size allocated for the JVM, the application may become unresponsive or crash.

See our detailed blog post about Java Virtual Machine Garbage Collection and Its Performance Impact

4. Code-Level Issues

Code-level issues in Java are problems that are caused by inefficient or poorly optimized code. These issues can result in poor application performance, higher resource consumption, and poor user experience. To address code-level issues, developers need to carefully analyze the code and optimize it for performance. This may involve removing unnecessary loops, managing memory allocation, optimizing algorithms and data structures, and managing I/O operations.

5. Pool Connections

In Java, a pool connection is a technique used to reuse database connections instead of creating a new connection for each request. This can improve the performance of an application by reducing the overhead associated with creating and destroying database connections.

When a database connection is requested, it takes time to establish the connection to the database server and to authenticate the user credentials. Creating a new connection for each request can add a significant amount of overhead and slow down the application’s performance. By using a pool connection, the application can reuse a connection that has already been established and authenticated, which can significantly reduce the overhead associated with establishing new connections.

However, if pool connections are not managed properly, they can also cause performance issues. For example, if there are too few connections in the pool, the application may need to wait for a connection to become available, which can cause delays and slow down the application’s performance. On the other hand, if there are too many connections in the pool, it can cause excessive resource consumption and slow down the database server.

Related content: Read our guide to Java Profiling

How Java Performance Tuning Works

Java performance tuning is important because it can significantly impact the speed, efficiency, and scalability of Java-based applications. Optimizing performance can improve user experience, reduce hardware requirements, and increase the overall productivity and profitability of an application.

Garbage collection is an important process in Java applications, as it manages the allocation and deallocation of memory. Tuning the garbage collection process can improve performance by reducing the amount of time spent on garbage collection and minimizing the impact of garbage collection on throughput and latency.

Here are some steps to improve the performance of Java applications.

Choose the Performance Parameters to Tune

Choosing which performance parameters to tune depends on the specific requirements of the Java application and the resources available on the computer system. However, some basic parameters that can be tuned to improve Java performance include:

  • Footprint: The amount of memory and CPU resources consumed by a Java application. Tuning the footprint involves minimizing the amount of memory and CPU resources used by the application, which can improve performance by reducing the amount of time spent on garbage collection and other memory management tasks.
  • Throughput: The amount of work that can be performed by a Java application within a given period of time. Tuning throughput involves optimizing the application’s algorithms, data structures, and I/O operations to maximize the amount of work that can be performed efficiently.
  • Latency: The time it takes for a Java application to respond to user requests. Tuning latency involves minimizing the response time of the application by optimizing the code, reducing network latency, and improving resource allocation.

However, these parameters are interrelated, and tuning one parameter may affect the others. For example, combining low memory usage with high throughput increases latency. Therefore, it is important to prioritize and balance the parameters based on the specific requirements of the application and the available resources.

Identify the System’s Limits

Identifying the system’s maximum capacity is important to ensure that the system can handle the expected workload and to avoid performance issues. This can be done by load testing the system with increasing workloads until it reaches its maximum capacity, at which point the system may start to exhibit performance issues such as increased response time or decreased throughput. The maximum capacity can then be determined based on the workload at which these issues start to appear.

Use a Profiler to Handle Bottlenecks 

A Java profiler is a tool that can assist in identifying performance bottlenecks in a Java application. Most bottlenecks result from the limitations of major shared resources, such as memory, CPU, input/output operations, and threads. 

To use a Java profiler to identify bottlenecks, one should set it up to monitor the Java application during runtime and then run the application under normal user load. Next, collect and analyze the profiling data generated by the profiler to identify methods, classes, and components that consume the most CPU time, memory, and I/O resources. Look for patterns and correlations in the profiling data to pinpoint potential performance bottlenecks, and investigate the code and system components that are causing them. 

Create a Performance Test Suite

Creating a performance test suite for a Java application helps ensure that it meets the performance requirements of its intended use. To create a performance test suite, developers should first define the performance requirements of the application. Next, they should design a set of tests that simulate realistic user workloads and measure key performance metrics, such as response time and throughput. 

The test suite should be executed under varying conditions, such as high user loads and different system configurations, to ensure that the application performs well under all expected scenarios. 

8 Tips for Optimizing and Improving Java Performance 

1. Avoid Writing Long Methods

In Java, a long method is a method that contains a large number of lines of code, making it more difficult to read, maintain, and test. Long methods can be a performance bottleneck, as they can be difficult to optimize and can lead to poor application performance. 

To avoid writing long methods in Java, developers should follow the Single Responsibility Principle (SRP), which states that each method should have a single responsibility and focus on a specific task or functionality. Additionally, developers can use refactoring techniques to break down long methods into smaller, more manageable chunks, such as by extracting methods or creating new classes.

2. Use PreparedStatement instead of Statement

PreparedStatement is a more efficient way to execute SQL queries in Java than the Statement class. This is because PreparedStatement can precompile the SQL statement, which can improve performance by reducing the amount of time it takes to execute the query. Additionally, PreparedStatement can also help to prevent SQL injection attacks.

3. Use Caching

Caching is a technique that can be used to improve performance by storing frequently accessed data in memory. This can help to reduce the number of times that the data needs to be read from disk or the database, which can significantly improve performance. In Java, caching can be implemented using various frameworks such as Ehcache, Hazelcast, or Caffeine.

4. Use Stored Procedures Instead of Queries

Stored procedures are precompiled SQL statements that can be executed by the database server. They can be used to improve performance by reducing the amount of data that needs to be transmitted between the application and the database. Additionally, stored procedures can be more efficient than dynamically generated SQL queries, since they can be optimized by the database server.

5. Leverage StringBuilder

StringBuilder is a class in Java that allows developers to manipulate strings easily. It is used to create mutable string objects, which can be modified without creating new string objects. Java developers can use StringBuilder to make string concatenation easier by appending new strings to the existing StringBuilder object instead of creating new string objects each time a concatenation operation is performed. This can improve performance and reduce memory usage.

6. Optimize If-Else Statements 

If-else statements can affect Java performance because they require the JVM to evaluate each condition sequentially, which can slow down the execution of the code. To optimize the use of if-else statements, developers should try to use simpler conditions first and use short-circuit evaluation when possible. 

Additionally, developers can leverage switch statements instead of long chains of if-else statements to improve performance. Switch statements allow the JVM to jump directly to the relevant code block, rather than evaluating each condition sequentially, which can be faster for certain use cases.

7. Don’t Over-optimize

Over-optimization of Java performance can lead to code that is difficult to maintain and modify, which can hinder future development efforts. To avoid over-optimization, developers should focus on optimizing critical sections of the code and avoiding premature optimization. By optimizing only as needed, developers can keep the code clean and maintainable while still achieving good performance.

It’s also important to avoid over-engineering solutions to performance problems, which can lead to unnecessary complexity. Developers should start by profiling the application to identify bottlenecks, and then make incremental improvements to address those bottlenecks.

8. Use Java Profilers

Java profilers are tools that can be used to measure the performance of Java code. They can help to identify performance bottlenecks and provide insights into how to optimize performance. 

For example, Granulate’s continuous profiler is a free and open source Java profiler with an always-on approach. It samples the CPU, allowing you to investigate performance at any given time to see the impact of version releases, understand the performance impact of new features, compare deployments and isolate performance issues. 

By continuously analyzing code performance across your entire environment, you can optimize the most resource-consuming parts of your code, improve application performance, and reduce costs. 

Learn more about Granulate’s continuous profiler.

See Additional Guides on Key Performance Testing Topics

Together with our content partners, we have authored in-depth guides on several other topics that can also be useful as you explore the world of performance testing.

Application Performance Monitoring

Authored by Granulate

Image Optimization

Authored by Cloudinary

Optimizing Python

Authored by Granulate

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