Java 21 Features – What's New in the Java Release

Java has remained a trusted and widely adopted programming language for more than 20 years. Each new Java release brings enhanced capabilities that simplify development and improve performance and security. In September 2023, Java 21 was released (also known as JDK 21). As a Long-Term Support (LTS) release, Java 21 will benefit from extended updates and maintenance. Java 21 Features – What's New in the Java Release: Explore virtual threads, pattern matching, and other key enhancements in the latest Java 21 update.

In this blog, we will explore the top features introduced in Java 21, how they help developers, and why you should consider upgrading to this version.

Why Java 21 is Important?

Let’s understand why Java 21 matters.

• • Java 21 is an LTS version (previous ones were Java 17 and Java 11).
• • LTS versions are more stable and widely adopted in companies.
• • Java 21 includes many preview features that are now finalized.
• • It brings improvements in performance, syntax, and security.

In this blog, we will explore the top features introduced in Java 21, how they help developers, and why you should consider upgrading to this version.

List of Key Features in Java 21

Here’s a quick look at the most important features in Java 21:

1. 1. String Templates (Preview)
2. 2. Record Patterns (Final)
3. 3. Pattern Matching for Switch (Final)
4. 4. Virtual Threads (Final)
5. 5. Sequenced Collections (Final)
6. 6. Scoped Values (Preview)
7. 7. Foreign Function & Memory API (Final)
8. 8. Unnamed Classes and Instance Main Methods (Preview)
9. 9. Deprecation of Finalization
10. 10. Performance Improvements

Now, let's dive deeper into these features and understand how they can benefit Java developers.

 1. String Templates (Preview)

This is one of the most exciting features in Java 21. This feature introduces template strings, which streamline how developers format and manage strings in Java.

Before Java 21: -

String name = "Rahul";

int age = 25;

String info = "My name is " + name + " and I am " + age + " years old.";

With String Templates:

String name = "Rahul";

int age = 25;

String info = STR."My name is \{name} and I am \{age} years old.";

➡ It reduces boilerplate code and improves readability.

2. Record Patterns (Final)

Record patterns provide a concise way to break down object data within Java programs. This feature was in preview earlier and is now finalized in Java 21.

Example:

record Person (String name, int age) {}

void printPerson(Object obj) { 

    if (obj instanceof Person(String name, int age)) {

        System.out.println(name + " is " + age + " years old.");

    }

}

➡ It simplifies how we extract data from objects using instanceof.

3. Pattern Matching for switch (Final)

Java 21 enhances switch statements with direct type matching, resulting in cleaner and safer logic.

Example:

static void printValue(Object obj) {

    switch (obj) {

        case String s -> System.out.println("String: " + s);

        case Integer i -> System.out.println("Integer: " + i);

        default -> System.out.println("Unknown type");

    }

}

➡ This avoids unnecessary casting and improves type safety.

🔸 4. Virtual Threads (Final)

This is a game-changer for concurrent programming in Java.

• Virtual threads are a new kind of lightweight thread designed for efficient concurrency.
• They allow you to create thousands of threads with low memory.
• Ideal for scalable server applications.

Before:

new Thread(() -> runTask()).start();

Now:

Thread.startVirtualThread(() -> runTask());

➡ Improves performance in highly concurrent systems like servers.

5. Sequenced Collections (Final)

A new interface added: SequencedCollection, SequencedSet, and SequencedMap.

• These collections maintain a consistent sequence of elements, improving reliability.
• You can easily get the first and last elements.

Example:

SequencedSet<String> names = new LinkedHashSet<>();

names.add( "A" );

names.add("B");

System.out.println(names.getFirst()); // A

System.out.println(names.getLast());  // B

➡ Useful when the order of elements matters.

6. Scoped Values (Preview)

Scoped values provide a safer and more efficient way to share data across threads, replacing ThreadLocal in many cases.

• More efficient than ThreadLocal
• Helps in structured concurrency

➡ Still in preview, but useful in concurrent programming.

🔸 7. Foreign Function & Memory API (Final)

This API allows Java programs to interact with native code (like C/C++) without using JNI (Java Native Interface).

• You can call native libraries more easily.
• Useful for performance-critical applications.

➡ Improves Java's ability to work with system-level code.

8. Unnamed Classes and Instance Main Methods (Preview)

Perfect for beginners or quick testing.

Java 21 lets you write simpler code by removing the need to define full classes for basic programs.

Old Way:

public class Hello {

    public static void main(String[] args) {

        System.out.println("Hello World");

    }

}

New Way:

void main() {

    System.out.println("Hello World");

}

➡ Makes Java more beginner-friendly and script-like.

9. Deprecation of Finalization

Java 21 officially deprecated finalization (using the finalize() method).

• Finalization has long been known for being unreliable and slow, which is why it's being phased out.
• Developers should use try-with-resources or the Cleaner API instead.

➡ Makes Java memory management more modern and efficient.

10. Performance & Security Improvements

Along with new features, Java 21 also brings:

• Better Garbage Collection (GC) performance
• Faster Startup time
• Improved Security features
• Smaller memory usage with virtual threads

Summary of Java 21 Features

Should You Upgrade to Java 21?

If you're using an older version like Java 8 or 11, Java 21 is a major upgrade. Being an LTS version, it’s stable and future-proof. Companies and developers are encouraged to migrate because of:

• Long-term support
• Better performance
• Modern syntax
• Easier concurrent programming

📝 Final Thoughts

Java 21 shows how Java continues to evolve while staying true to its principles — readability, reliability, and performance. Whether you are a beginner or an experienced developer, these new features can help you write better, faster, and more scalable Java applications.

Start using Java 21 in your upcoming projects to experience its modern and productive features.

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Author:-

Aarti Choudhary