Java 17 Features Every Developer Should Know

Java 17 is a Long-Term Support (LTS) release that brings significant improvements and new features. Here are the key features every Java developer should know:

1. Sealed Classes (JEP 409)

Sealed classes restrict which other classes or interfaces may extend or implement them:

public abstract sealed class Shape
    permits Circle, Rectangle, Triangle {
  // ...
}

public final class Circle extends Shape {
  // Only Circle, Rectangle, Triangle can extend Shape
}

2. Pattern Matching for switch (JEP 406)

Enhanced pattern matching capabilities in switch expressions:

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();
};

3. New Random Number Generators

Introduces new interface types for random number generation:

RandomGenerator generator = RandomGenerator.getDefault();
int randomInt = generator.nextInt(100);

4. Enhanced Pseudo-Random Number Generators

New interface for PRNG algorithms with better performance and thread safety.

5. Deprecation of Security Manager

The Security Manager is deprecated for removal, reflecting modern deployment practices.

Java 17 continues to improve performance, security, and developer productivity while maintaining backward compatibility.