Java 21, the latest release of the Java programming language, brings a wealth of new features and improvements, solidifying its position as a cornerstone of modern software development. Whether you are a seasoned developer or just starting, Java 21 offers tools and enhancements designed to elevate your coding experience.
1. Pattern Matching for Switch Expressions (Finalized)
The long-awaited feature, pattern matching for switch, is now finalized in Java 21. This allows developers to write concise, readable, and type-safe code when working with complex conditional logic.
Example:
public String formatShape(Object shape) {
return switch (shape) {
case Circle c -> "Circle with radius " + c.radius();
case Rectangle r -> "Rectangle with dimensions " + r.width() + " x " + r.height();
default -> "Unknown shape";
};
}Why It Matters:
This feature reduces boilerplate code and makes switch more powerful and versatile.
2. Record Patterns
Java 21 introduces record patterns, which simplify extracting values from record objects, further improving readability and reducing redundancy in your code.
Example:
record Point(int x, int y) {}
public boolean isOrigin(Point point) {
return switch (point) {
case Point(0, 0) -> true;
default -> false;
};
}Why It Matters: Record patterns streamline working with immutable data objects, making Java more functional and expressive.
3. Virtual Threads (Project Loom)
Virtual threads, a revolutionary feature from Project Loom, are now fully supported in Java 21. Virtual threads make it possible to create millions of threads without worrying about performance bottlenecks.
Example:
try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
IntStream.range(0, 10_000).forEach(i ->
executor.submit(() -> System.out.println("Task " + i))
);
}Why It Matters: Virtual threads radically simplify the development of high-throughput, scalable applications by decoupling thread creation from system resource constraints.
4. Scoped Values (Incubator)
Scoped values provide a lightweight mechanism for sharing immutable data within and across threads.
Example:
ScopedValue<String> user = ScopedValue.newInstance();
ScopedValue.where(user, "Alice").run(() -> {
System.out.println("Current user: " + user.get());
});
Why It Matters: Scoped values offer an elegant solution for thread-local data management without the overhead of traditional thread-local variables.
5. Sequenced Collections
Java 21 introduces sequenced collections, a new collection type that maintains the order of elements. This feature extends Set and Map with SequencedSet and SequencedMap interfaces.
Example:
SequencedSet<String> names = SequencedCollections.newSequencedSet();
names.add("Alice");
names.add("Bob");
names.reversed().forEach(System.out::println);
Why It Matters: Sequenced collections enhance the utility of Java collections, providing developers with more options for ordered data structures.
6. String Templates (Preview)
String templates simplify the creation of formatted strings by embedding expressions directly within them.
Example:
String name = "Alice";
int age = 30;
System.out.println(STR."My name is \{name} and I am \{age} years old.");Why It Matters:
This feature eliminates the verbosity of String.format and improves the clarity of string interpolation in Java.
7. Performance and JVM Improvements
Java 21 also includes significant performance optimizations, especially in the Just-In-Time (JIT) and Garbage Collection (GC) systems. Improvements in the ZGC and G1 collectors reduce pause times and increase throughput.
Why It Matters: Better JVM performance translates to faster and more responsive applications, with reduced resource consumption.
8. Deprecations and Removals
With each new release, some older features are deprecated or removed to streamline the platform and encourage best practices.
Key Changes in Java 21:
- Deprecated APIs: Removal of outdated methods and classes.
- Gradual phasing out of old JavaFX components.
What You Should Do: Check the release notes and update your code to stay compatible.
Conclusion
Java 21 is a feature-packed release that caters to modern development needs, from enhanced syntax with pattern matching and record patterns to revolutionary features like virtual threads and scoped values. These improvements not only simplify coding but also boost application performance and scalability. Upgrade to Java 21 today to unlock the full potential of the latest advancements in the Java ecosystem.