Java 17: Features

Released in September 2021, Java 17 marked a major milestone in the language’s modernization. It didn’t just bring stability to features tested in previous versions; it refined the syntax to be more concise, secure, and performant. It’s essentially the bridge between “Old Java” and the high-performance, modern syntax we use today.

Here is a summary of the most impactful features every developer should know:

1. Sealed Classes

You now have total control over your object hierarchy. With Sealed Classes, you can specify exactly which classes are permitted to inherit from another. This improves security and allows the compiler to perform exhaustive analysis in switch blocks.

sealed abstract class Transport permits Car, Motorbike {}

2. Records (Data Classes)

While they appeared in earlier versions, Java 17 consolidated Records as the standard way to create immutable data classes. A Record eliminates almost all boilerplate code like getters, toString(), equals(), and hashCode().

With just one line, you have a fully functional class. It’s Java’s answer to data classes in Kotlin or Scala.

record User(String name) {}

3. Pattern Matching for switch (Preview)

This feature transformed how we write conditionals. Now, a switch doesn't just evaluate values—it evaluates object types.

Say goodbye to verbose instanceof checks. You no longer have to ask if an object is a specific type and then manually cast it; the switch handles the casting for you in a single line.

static String formatter(Object o) {
  return switch (o) {
     case Integer i -> String.format("It's an integer: %d", i);
     case String s  -> String.format("It's text: %s", s);
     case null      -> "It's null";
     default        -> "Unknown type";
  };
}

Performance and Housekeeping

• G1 Garbage Collector: Faster, more efficient, and better at memory management.
• Deprecations: Applets are removed, and the Security Manager is being prepared for its final exit.
• Apple Silicon Support: Native optimization for Apple’s M1, M2, and M3 processors.
• Strict Floating-Point Semantics: Restored consistency in floating-point mathematical calculations across all platforms, making the strictfp keyword obsolete.
• Pseudo-Random Number Generators: Added the RandomGenerator interface, which unifies and modernizes how we generate random numbers, making it easy to swap algorithms.