Java 17 Features

Java 17, released in September 2021, is a Long-Term Support (LTS) version and brings exciting updates and modern language enhancements. Let’s take a look at the top features every Java developer should know.

1. Sealed Classes

Sealed classes let you restrict which classes can extend or implement a class or interface.

public sealed class Shape permits Circle, Square {}

final class Circle extends Shape {}
final class Square extends Shape {}

This gives you more control over class hierarchies and improves readability and maintainability.

2. Pattern Matching for instanceof

Simplifies type casting when using instanceof checks:

if (obj instanceof String s) {
    System.out.println(s.toUpperCase());
}

No need for manual casting anymore!

3. Switch Expressions (Standard)

Switch expressions were finalized in Java 17, enabling more concise syntax:

String result = switch (day) {
    case MONDAY, FRIDAY -> "Workday";
    case SATURDAY, SUNDAY -> "Weekend";
    default -> "Unknown";
};

4. Text Blocks (Standard)

Text blocks make multi-line strings easier to read and write:

String json = """
{
  "name": "Java",
  "version": 17
}
""";

No more escaping quotes or newlines manually!

5. New Record Enhancements

Records, introduced in Java 14 and finalized in Java 16, now support better pattern matching and can be used with sealed types:

public record Point(int x, int y) {}

They reduce boilerplate for simple data carriers.

6. JEP 356: Enhanced Pseudo-Random Number Generators

A new set of interfaces and implementations for flexible and streamable random number generation:

RandomGenerator gen = RandomGeneratorFactory.of("L64X128MixRandom").create();
System.out.println(gen.nextInt());

7. Strong Encapsulation of JDK Internals

Java 17 strongly encapsulates internal APIs. If you relied on sun.* packages, you’ll need to migrate to public APIs.

8. Deprecations and Removals

• Removal of the Applet API
• Deprecation of the Security Manager
• Removal of RMI Activation system

📌 Final Thoughts

Java 17 brings modern language features, performance improvements, and better developer ergonomics — and as an LTS release, it’s built for stability.

Time to upgrade? If you're on Java 8 or even Java 11, Java 17 is a smart step forward.