Java 21: A Comprehensive Overview of the Latest Features

Java 21: A Comprehensive Overview of the Latest Features


Java, one of the most enduring and widely used programming languages, continues to evolve with each new version. The release of Java 21 marks another significant step in its journey, introducing a variety of features and updates that enhance its functionality, performance, and ease of use. In this blog post, we will delve into the key features of Java 21, offering examples and explanations to help developers understand and utilize these new additions effectively.

1. Pattern Matching for Switch (Preview)

Pattern Matching has been one of the most anticipated features in Java, and in Java 21, it takes another step forward with its integration into the switch statement. This feature allows developers to write more concise and readable code.


Object obj = // …;

String formatted = switch (obj) {

    case Integer i -> String.format(“int %d”, i);

    case Long l    -> String.format(“long %d”, l);

    case Double d  -> String.format(“double %f”, d);

    case String s  -> String.format(“String %s”, s);

    default        -> obj.toString();


2. Record Patterns (Preview)

Record Patterns, in conjunction with Pattern Matching, provide a powerful way to deconstruct records. This feature simplifies the extraction and handling of information from records.


record Point(int x, int y) {}

public static String classify(Object o) {

    return switch (o) {

        case Point(int x, int y) -> String.format(“Point at (%d, %d)”, x, y);

        default -> “Unknown”;



3. Virtual Threads (Incubator)

One of the most revolutionary features in Java 21 is the introduction of Virtual Threads. This feature aims to simplify concurrent programming by making lightweight threads that can be handled in massive numbers without the overhead of traditional threads.


try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {

    executor.submit(() -> {

        // Task here



4. Foreign Function & Memory API (Incubator)

Continuing from previous versions, Java 21 enhances the Foreign Function & Memory API. This feature provides a safer, more efficient way to interact with native code and memory, which is crucial for certain types of high-performance applications.


try (var session = MemorySession.openConfined()) {

    var segment = MemorySegment.allocateNative(100, session);

    // Operations on the native memory


5. Improved Random Number Generators

Java 21 introduces new interfaces and implementations for Random Number Generators (RNG). These improvements offer more flexibility and better performance for various RNG requirements.


RandomGenerator rng = RandomGenerator.of(“Xoshiro256PlusPlus”);

int randomValue = rng.nextInt();

6. API Enhancements

Java 21 also includes several API enhancements that improve existing features and add new capabilities. These include updates to the Stream API, Collections, and more, making standard library usage more intuitive and powerful.


List<String> list = List.of(“Java”, “Python”, “C++”);;


Java 21 is a testament to Java’s enduring commitment to innovation and improvement. The introduction of features like Pattern Matching for switch, Record Patterns, Virtual Threads, and enhanced APIs, among others, demonstrates Java’s ongoing evolution to meet the modern developer’s needs. As these features get refined and eventually become standard, they will undoubtedly make Java an even more powerful tool in the developer’s arsenal.

For Java developers, it’s essential to stay updated with these changes and experiment with the new features. Java’s future looks bright, and Java 21 is a significant milestone in its continuous journey of growth and adaptation.

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