Introduction to Java 25

Java 25 is a significant release in the Java ecosystem, bringing numerous **performance improvements** and new features to the table. One of the most notable features is the introduction of **stable virtual threads**, which aim to simplify concurrent programming in Java. The java.lang.Thread class has been updated to support virtual threads, allowing developers to write more efficient and scalable code. This feature is a major step forward in making Java a more competitive language for concurrent programming.

The **Java Virtual Machine (JVM)** has also undergone significant changes in Java 25, with a focus on improving **garbage collection** and **memory management**. The new G1 garbage collector has been optimized for low-pause-time garbage collection, making it suitable for real-time systems and other applications that require predictable performance. Additionally, the **Java Memory Model** has been updated to provide better support for concurrent programming and to reduce the risk of memory-related bugs.

For developers looking to take advantage of Java 25’s new features, it’s essential to have a solid understanding of **concurrent programming** concepts and the **java.util.concurrent** package. Our article on Mastering Java Concurrency provides a comprehensive introduction to these topics and can serve as a useful primer for exploring Java 25’s capabilities. By leveraging Java 25’s **stable virtual threads** and other features, developers can create more efficient, scalable, and reliable applications.

The release of Java 25 marks a significant milestone in the evolution of the Java ecosystem, and its impact will be felt across a wide range of industries and applications. As developers begin to explore the new features and capabilities of Java 25, they will be able to create more complex, scalable, and performant systems, driving innovation and growth in the Java community. With its **strong focus on performance and concurrency**, Java 25 is an exciting release that is sure to have a lasting impact on the world of Java development.

Prerequisites for Java 25 Adoption

To leverage the features of Java 25, particularly **stable virtual threads**, your system must meet specific requirements. The minimum **JDK** version required is Java 25, and it is recommended to use the latest version of your preferred **IDE**. For this tutorial, we will be using **Eclipse**.

Before proceeding, ensure you have a good understanding of **multithreading** concepts, as virtual threads are an extension of this concept. If you need a refresher, visit our Java Multithreading Basics article for more information.

The **Java 25** release brings significant performance improvements, including **virtual threads**, which are designed to reduce the overhead of thread creation and management. To demonstrate the benefits of virtual threads, consider the following example:

public class VirtualThreadExample {
 public static void main(String[] args) {
 // Create a virtual thread
 Thread.startVirtualThread(() -> {
 // Simulate some work
 try {
 Thread.sleep(1000); // sleep for 1 second
 } catch (InterruptedException e) {
 Thread.currentThread().interrupt(); // restore interrupted status
 }
 System.out.println("Virtual thread completed");
 });
 // Continue with the main thread
 System.out.println("Main thread continuing");
 }
}

The expected output will be:

Main thread continuing
Virtual thread completed

This example demonstrates how virtual threads can be used to run tasks concurrently without the overhead of traditional threads. For more information on **concurrency** in Java, visit our Java Concurrency Tutorial.

To take full advantage of Java 25’s performance improvements, it is essential to understand how to **profile and optimize** your applications. Our Java Performance Optimization article provides guidance on how to identify and address performance bottlenecks in your code.

Deep Dive into Stable Virtual Threads

Java 25 introduces stable virtual threads, a new type of thread that provides significant performance improvements over traditional threads. A virtual thread is a lightweight thread that is scheduled by the Java runtime, rather than the operating system. This allows for more efficient use of system resources, as the Java runtime can manage the threads more effectively. The Thread class has been updated to support virtual threads.

The key benefit of stable virtual threads is that they can be used to write high-performance concurrent code without the need for low-level threading APIs. This makes it easier for developers to write concurrent code, as they do not need to worry about the underlying threading mechanics. For more information on concurrent programming in Java, see our article on Java Concurrency Basics. The java.lang.Thread class provides a range of methods for working with virtual threads, including the start() method.

One of the main differences between stable virtual threads and traditional threads is the way they are scheduled. Traditional threads are scheduled by the operating system, which can lead to context switching overhead. Virtual threads, on the other hand, are scheduled by the Java runtime, which can reduce context switching overhead and improve performance. The java.lang.Runtime class provides methods for working with the Java runtime, including the availableProcessors() method.

The use of stable virtual threads can also simplify the development of concurrent applications, as developers do not need to worry about the underlying threading mechanics. This makes it easier to write concurrent code, as developers can focus on the logic of the application rather than the threading details. To learn more about how to use stable virtual threads in your applications, see our article on Java Virtual Threads Best Practices. The java.util.concurrent package provides a range of classes for working with concurrent applications, including the ExecutorService class.

Migrating to Java 25: A Step-by-Step Guide

To migrate existing applications to Java 25, you need to update your project’s **JDK** version and modify the code to utilize the new features, such as virtual threads. Start by updating your project’s build configuration to use Java 25. You can do this by changing the **java.version** property in your pom.xml file if you’re using Maven, or the **sourceCompatibility** property in your build.gradle file if you’re using Gradle.

The next step is to identify areas of your code that can benefit from **virtual threads**. Look for methods that perform I/O operations or other blocking tasks, as these can be executed concurrently using virtual threads. For example, you can use the **Thread.startVirtualThread** method to create a new virtual thread.
For more information on Java concurrency, you can refer to our previous tutorial.

Here’s an example of how you can use virtual threads to execute a blocking task:

public class VirtualThreadExample {
 public static void main(String[] args) {
 // Create a new virtual thread
 Thread virtualThread = Thread.startVirtualThread(() -> {
 // Simulate a blocking task
 try {
 Thread.sleep(1000); // sleep for 1 second
 } catch (InterruptedException e) {
 Thread.currentThread().interrupt(); // restore interrupted status
 }
 System.out.println("Virtual thread finished");
 });
 
 // Continue executing the main thread
 System.out.println("Main thread finished");
 }
}

The expected output of this program will be:

Main thread finished
Virtual thread finished

As you can see, the main thread continues executing without blocking, while the virtual thread executes the blocking task concurrently. For further reading on Java 25 features, you can refer to our article on the subject.

Real-World Example: Leveraging Stable Virtual Threads

To demonstrate the benefits of **stable virtual threads**, consider a web server that handles multiple requests concurrently. By utilizing virtual threads, we can improve the performance and responsiveness of the server. The java.lang.Thread class provides the necessary functionality to create and manage threads.

The following example showcases a simple web server that leverages **stable virtual threads** to handle incoming requests. This server will create a new **virtual thread** for each incoming request, allowing it to handle multiple requests concurrently. For more information on **concurrency** and **parallelism**, refer to our article on Java Concurrency Tutorial.

public class VirtualThreadServer {
 public static void main(String[] args) {
 // Create a new server that listens for incoming requests
 var server = new com.sun.net.httpserver.HttpServer();
 // Create a new context for handling requests
 server.createContext("/request", exchange -> {
 // Create a new virtual thread to handle the request
 Thread.startVirtualThread(() -> {
 // Handle the request
 var response = "Request received";
 exchange.sendResponseHeaders(200, response.length());
 // Send the response back to the client
 exchange.getResponseBody().write(response.getBytes());
 exchange.getResponseBody().close();
 });
 });
 // Start the server
 server.setExecutor(null); // Use the default executor
 server.start();
 }
}

When running this server, you can use a tool like `curl` to send requests to the server. The expected output will be the response from the server, which in this case is “Request received”.

Request received

This example demonstrates how **stable virtual threads** can be used to improve the performance and responsiveness of a web server. By leveraging **virtual threads**, the server can handle multiple requests concurrently, improving overall throughput. For further reading on **Java 25** and its features, refer to our article on Java 25 Features.

Performance Improvements in Java 25

Java 25 introduces significant performance enhancements that improve the overall efficiency of Java applications. One of the key features is the stable virtual threads which enable developers to write high-throughput concurrent code with minimal overhead. The Thread class has been optimized to reduce the creation and management of threads, resulting in improved multithreading capabilities. For more information on concurrency in Java, visit our Java Concurrency Basics tutorial.

The benchmarking process in Java 25 has also been revamped, providing more accurate and reliable results. The java.lang.System class now includes methods for measuring execution time and memory usage, making it easier to identify performance bottlenecks. Developers can use these methods to optimize their code and improve overall application performance. By leveraging these optimization techniques, developers can create high-performance Java applications that meet the demands of modern computing.

To take full advantage of Java 25’s performance improvements, developers should focus on profiling and optimizing their code. The java.lang.management package provides a range of classes and methods for monitoring and managing Java applications, including the ManagementFactory class. By using these tools and techniques, developers can identify and address performance issues, resulting in faster and more efficient Java applications. For further reading on Java performance tuning, visit our Java Performance Tuning guide.

The just-in-time (JIT) compiler in Java 25 has also been improved, providing better code optimization and cache management. The java.lang.Compiler class allows developers to interact with the JIT compiler, enabling them to fine-tune their application’s performance. By combining these features with the new virtual threads and concurrency APIs, developers can create high-performance Java applications that are both efficient and scalable.

Common Mistakes to Avoid in Java 25

Java 25 introduces **virtual threads**, which can significantly improve the performance of concurrent applications. However, developers must be aware of common pitfalls when working with these new features. One of the most critical aspects is understanding how to properly use **Thread.start()** and **Thread.join()**.

Mistake 1: Incorrectly Starting Virtual Threads

When starting a virtual thread, it’s essential to ensure that the **Thread** instance is properly configured. The following example demonstrates a common mistake:

public class VirtualThreadExample {
 public static void main(String[] args) {
 // WRONG
 Thread thread = new Thread(() -> System.out.println("Hello from virtual thread"));
 thread.start(); // This will throw an exception because the thread is not a virtual thread
 }
}

The above code will throw an exception because the **Thread** instance is not a virtual thread. The correct way to start a virtual thread is to use the **Thread.startVirtualThread()** method. For more information on **virtual threads**, refer to our article on Introduction to Java 25 Virtual Threads.

Mistake 2: Insufficient Synchronization

When working with concurrent applications, **synchronization** is crucial to prevent data corruption and ensure thread safety. The following example demonstrates a common mistake:

public class SynchronizationExample {
 private static int counter = 0;
 public static void main(String[] args) throws InterruptedException {
 // WRONG
 Thread thread1 = new Thread(() -> {
 for (int i = 0; i < 10000; i++) {
 counter++; // This operation is not thread-safe
 }
 });
 Thread thread2 = new Thread(() -> {
 for (int i = 0; i < 10000; i++) {
 counter++; // This operation is not thread-safe
 }
 });
 thread1.start();
 thread2.start();
 thread1.join();
 thread2.join();
 System.out.println(counter);
 }
}

The above code will produce incorrect results because the **counter** variable is not properly synchronized. To fix this issue, you can use the **synchronized** keyword or a **Lock** object. For more information on **concurrency** and **synchronization**, refer to our article on Java Concurrency Basics.

Corrected Code

Here's the corrected version of the previous example:

public class SynchronizationExample {
 private static int counter = 0;
 public static void main(String[] args) throws InterruptedException {
 Thread thread1 = new Thread(() -> {
 for (int i = 0; i < 10000; i++) {
 synchronized (SynchronizationExample.class) { // Synchronize access to the counter variable
 counter++;
 }
 }
 });
 Thread thread2 = new Thread(() -> {
 for (int i = 0; i < 10000; i++) {
 synchronized (SynchronizationExample.class) { // Synchronize access to the counter variable
 counter++;
 }
 }
 });
 thread1.start();
 thread2.start();
 thread1.join();
 thread2.join();
 System.out.println(counter);
 }
}

Expected output:
20000

By following best practices and avoiding common mistakes, developers can effectively utilize Java 25's **virtual threads

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ConcurrentTest {
 public static void main(String[] args) {
 // Create an executor service with 5 virtual threads
 ExecutorService executor = Executors.newVirtualThreadPerTaskExecutor();
 // Submit 10 tasks to the executor
 for (int i = 0; i < 10; i++) {
 // Each task simply prints its index
 int index = i; // capture the index in a local variable
 executor.submit(() -> {
 System.out.println("Task " + index + " executed");
 // Simulate some work
 try {
 Thread.sleep(100);
 } catch (InterruptedException e) {
 Thread.currentThread().interrupt();
 }
 });
 }
 // Shut down the executor
 executor.shutdown();
 }
}

Task 0 executed
Task 1 executed
Task 2 executed
Task 3 executed
Task 4 executed
Task 5 executed
Task 6 executed
Task 7 executed
Task 8 executed
Task 9 executed