Java Virtual Threads is a new feature introduced in Java 19 that allows developers to create lightweight threads, also known as fibers, that can run concurrently within a single operating system thread. This can improve the scalability and efficiency of Java applications, particularly those that need to handle a large number of client connections or concurrent requests.
Virtual threads are implemented using a technique known as Continuation Passing Style (CPS). CPS is a programming paradigm that involves passing the control flow of a program between different sections of code, rather than relying on a central thread of execution. This allows virtual threads to be created and managed more efficiently than traditional threads. You can also check this article for more details.
Table Of Contents
1. Diferrences Between Virual Threads and Java Threads
Virtual threads are distinct from traditional Java threads in several ways. First, they are created using a new API called the VirtualThreadFactory, which provides a simplified interface for managing and scheduling virtual threads. Second, they have much lower memory overhead compared to traditional threads, making it possible to create many more of them without exhausting system resources. Finally, they are designed to work seamlessly with existing Java code, so developers can start using virtual threads without having to rewrite their entire application.
To create a virtual thread, you can use the VirtualThreadFactory class, which provides several factory methods for creating virtual threads with different characteristics. For example, you can create a virtual thread that executes a Runnable or Callable task, or one that runs indefinitely until it is explicitly stopped.
Here’s an example of how to create a virtual thread:
VirtualThreadFactory factory = VirtualThreadFactory.builder().user(false).daemon(true).build();
VirtualThread thread = factory.newThread(() -> {
System.out.println("Hello, world!");
});
thread.start();
In this example, we created a new virtual thread factory that produces daemon threads (i.e., threads that run in the background and don’t prevent the JVM from shutting down), and then use it to create a new virtual thread that prints “Hello, world!” to the console.
Virtual threads offer many benefits over traditional threads, but they also come with some trade-offs. For example, they may not be suitable for applications that require fine-grained control over thread scheduling or synchronization, and they may not work well with third-party libraries that rely on traditional threads. Nonetheless, Java Virtual Threads represent an exciting new development in Java concurrency that is likely to have a big impact on the way developers write concurrent code in the years to come.
2. How To Create Virtual Threads?
To create virtual threads in Java, you can use the VirtualThreadFactory class provided in the java.lang package. Here are the basic steps to create a virtual thread:
- Create an instance of the
VirtualThreadFactoryclass using theVirtualThreadFactory.builder()method. - Configure the factory with any desired options using the builder methods. For example, you can set the thread name prefix, whether the threads should be daemon threads, or whether they should be part of the user or system thread group.
- Use the
newThread()method of theVirtualThreadFactoryto create a new virtual thread. This method takes aRunnableorCallableobject that specifies the task to be executed by the thread. - Call the
start()method of the virtual thread to start its execution.
Here’s an example of how to create a virtual thread using the VirtualThreadFactory class:
VirtualThreadFactory factory = VirtualThreadFactory.builder()
.user(false)
.daemon(true)
.namePrefix("MyVirtualThread")
.build();
VirtualThread virtualThread = factory.newThread(() -> {
// Code to be executed by the virtual thread
});
virtualThread.start();
In this example, we created a VirtualThreadFactory instance with a few options set using the builder methods. We then create a new virtual thread using the newThread() method of the factory and passing a lambda expression that defines the code to be executed by the thread. Finally, we call the start() method of the virtual thread to start its execution.
Note that virtual threads have a much smaller memory footprint than regular threads, so you can create many more of them without exhausting system resources. However, you should still be mindful of the total number of threads in your application and ensure that you are not creating too many threads, which can lead to contention and reduced performance.
3. Advantages & Disadvantages of Java Virtual Threads
Java Virtual Threads (JVT) offer several advantages over traditional Java threads.
Here are some of the main advantages:
- Lower memory overhead: Virtual threads have a much smaller memory footprint than traditional threads, which means you can create many more of them without consuming excessive memory. This is because virtual threads share a stack with other threads, reducing the amount of memory needed for each thread.
- Improved scalability: Because virtual threads have a lower memory overhead, they are more scalable than traditional threads. You can create more virtual threads without running into memory constraints, which can help improve the performance of your application.
- Better utilization of system resources: With virtual threads, you can create many more threads without exhausting system resources such as CPU time, thread handles, and kernel-level threads. This can help you achieve better utilization of system resources and improve the efficiency of your application.
- Easier programming model: Virtual threads provide a simpler and more natural programming model than traditional threads. You can use familiar control structures such as loops and conditionals to write code that runs concurrently on virtual threads. This can make it easier to write and reason about concurrent code.
- Seamless integration with existing code: Virtual threads are designed to work seamlessly with existing Java code. You can use them in conjunction with other concurrency constructs such as executors, CompletableFuture, and Reactive Streams without having to rewrite your entire application.
While Java Virtual Threads (JVT) offer several advantages, they also have some potential disadvantages that developers should be aware of.
Here are some of the main disadvantages:
- Compatibility issues: Some existing Java libraries and frameworks may not be compatible with virtual threads, as they may rely on assumptions or APIs that are specific to traditional threads. This could make it difficult to adopt virtual threads in existing codebases, or require modifications to third-party libraries to work with virtual threads.
- Synchronization challenges: Virtual threads share a single underlying operating system thread, which means that synchronization between virtual threads may be more challenging than with traditional threads. Developers may need to carefully design their synchronization strategies to avoid race conditions or other synchronization issues.
- Debugging and profiling: Debugging and profiling virtual threads may be more challenging than with traditional threads, as they share the same underlying thread ID and other thread-related attributes. This could make it more difficult to identify and diagnose issues related to concurrency or thread contention.
- Limited control over scheduling: With virtual threads, the Java runtime is responsible for scheduling the threads, which can limit the level of control that developers have over thread scheduling. While the Java runtime is designed to provide efficient scheduling of virtual threads, there may be cases where more fine-grained control is needed.
- Performance trade-offs: While virtual threads are more lightweight than traditional threads, they may have some performance trade-offs. For example, switching between virtual threads may be slower than with traditional threads, which could impact the performance of certain types of applications.
4. Virtual Threads Performance Impact
Java Virtual Threads (JVT) can have a positive impact on the performance of certain types of applications, but their impact may vary depending on the specific use case. Here are some factors that can impact the performance of virtual threads:
- Task size: Virtual threads are optimized for executing small, short-lived tasks. If your application has many small tasks that can be executed concurrently, virtual threads may provide a significant performance boost over traditional threads.
- Contention: If your application has a high degree of contention between threads, virtual threads may help reduce contention and improve performance. This is because virtual threads are more lightweight than traditional threads, and can be created and destroyed more quickly.
- Synchronization: Synchronization between virtual threads can be more challenging than with traditional threads, and poorly designed synchronization strategies can lead to contention and decreased performance. Developers should carefully design their synchronization strategies to ensure efficient and effective synchronization between virtual threads.
- I/O operations: Virtual threads can be particularly effective for applications that perform a lot of I/O operations, such as network or database operations. This is because virtual threads are better suited to handling tasks that involve waiting for I/O operations to complete.
- Resource utilization: Virtual threads are more efficient in terms of memory utilization than traditional threads, which can help improve the overall resource utilization of your application. This can be particularly important for applications that need to run on systems with limited memory resources.
Overall, the performance impact of virtual threads will depend on the specific use case and the nature of the tasks being performed. Developers should carefully evaluate the potential benefits and trade-offs of virtual threads before deciding whether to use them in their applications. In general, virtual threads can provide a significant performance boost for applications with many small tasks or I/O operations, but may not provide as much benefit for applications with long-running tasks or high degrees of synchronization.
5. Wrapping Up
In conclusion, Java virtual threads are a relatively new feature in the Java programming language that provide an efficient way to manage lightweight threads. They are designed to be more efficient than traditional threads, which can be relatively heavy and can consume significant resources.
Virtual threads can be used to scale up the number of threads in a Java application without incurring the overhead associated with traditional threads. This makes them particularly useful for applications that need to handle a large number of concurrent connections.
Moreover, virtual threads can be used to simplify the development of asynchronous code, which can be difficult to write and maintain using traditional threads. Virtual threads make it easier to write code that executes asynchronously without sacrificing performance.
Overall, Java virtual threads are a promising development in the Java programming language, and they are likely to become increasingly popular as more developers become familiar with them and start to use them in their applications.
