🚀 Java 17 Features You Need to Know

Java 17 is a long-term support (LTS) release that introduces several modern features to improve code readability, performance, and safety. In this post, we’ll cover the most important features every Java developer should know, with examples.

1. Sealed Classes

Sealed classes allow you to restrict which classes can extend or implement a class/interface, making your hierarchy more controlled and safe.

// Define a sealed class
public sealed class Shape permits Circle, Rectangle { }

public final class Circle extends Shape { }

public final class Rectangle extends Shape { }

✅ Use Case: When you want to control all possible subclasses, useful in modeling finite hierarchies.

2. Pattern Matching for instanceof

Pattern matching simplifies type checks and casting.

Object obj = "Hello Java 17";

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

✅ Benefit: No more explicit casting, cleaner and safer code.

3. Records

Records are compact, immutable data classes.

public record Person(String name, int age) { }

Person p = new Person("Alice", 25);
System.out.println(p.name()); // Alice

✅ Use Case: DTOs, simple value objects, reducing boilerplate code.

4. switch Expressions

Switch is now more expressive and can return values.

String day = "MONDAY";
int numLetters = switch (day) {
    case "MONDAY", "FRIDAY" -> 6;
    case "TUESDAY" -> 7;
    default -> throw new IllegalArgumentException("Unknown day: " + day);
};

✅ Benefit: Fewer lines, more readable, safer.

5. Text Blocks

Text blocks allow multi-line strings without escaping quotes.

String json = """
{
    "name": "Alice",
    "age": 25
}
""";

✅ Use Case: Easier JSON, SQL, HTML embedding in code.

Conclusion

Java 17 brings many modern features that simplify code and improve readability. Start experimenting with sealed classes, records, pattern matching, and switch expressions to write cleaner, safer, and more maintainable Java code.

Labels for this post: Java, Java 17 Features, Interview Prep