Java 17 Features

Java 17 is a Long-Term Support (LTS) release that introduced several important language enhancements and JVM improvements. It became widely adopted in enterprise applications.

1. Sealed Classes

Sealed classes restrict which classes can extend or implement them.

public sealed class Shape
    permits Circle, Rectangle {}

final class Circle extends Shape {}

final class Rectangle extends Shape {}

2. Records

Records provide a concise way to create immutable data classes.

record Person(String name, int age) {}

Person p = new Person("John", 30);
System.out.println(p.name());

3. Pattern Matching for instanceof

Simplifies type checking and casting.

Object obj = "Hello";

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

4. Text Blocks

Text blocks allow writing multi-line strings easily.

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

System.out.println(json);

5. Enhanced Pseudo-Random Number Generators

Java 17 introduced new interfaces for generating random numbers.

RandomGenerator generator = RandomGenerator.getDefault();

int number = generator.nextInt(100);
System.out.println(number);

6. Improved Switch Expressions

Switch expressions became more powerful and concise.

int day = 2;

String result = switch(day) {
    case 1 -> "Monday";
    case 2 -> "Tuesday";
    default -> "Other";
};

System.out.println(result);

Quick Revision Summary