Java 17 Features

Java 17, released on September 14, 2021, is a Long-Term Support (LTS) release that brings significant enhancements to the Java language and platform. As an LTS version, Java 17 receives extended support until at least September 2029, making it an excellent choice for production applications.

This release introduces several powerful features that improve code quality, reduce boilerplate, and enhance developer productivity. Let’s explore the key features that make Java 17 a milestone release.

Key Features

• Sealed Classes

  Sealed classes provide fine-grained control over inheritance hierarchies by explicitly declaring which classes can extend or implement a type. This feature is perfect for modeling closed domain hierarchies and works beautifully with pattern matching.

public sealed class Shape permits Circle, Rectangle, Triangle {
    // Only Circle, Rectangle, and Triangle can extend Shape
}

public final class Circle extends Shape {
    private final double radius;
    // ...
}

Benefits:

• Better domain modeling with closed hierarchies
• Enhanced security by preventing unexpected subclassing
• Compile-time exhaustiveness checking with pattern matching

• Clearer API contracts

• Pattern Matching for instanceof

  This feature eliminates the redundant casting that traditionally follows an instanceof check by combining type testing with variable binding in a single operation.

// Before Java 17
if (obj instanceof String) {
    String str = (String) obj;
    System.out.println(str.length());
}

// With Java 17
if (obj instanceof String str) {
    System.out.println(str.length());
}

Benefits:

• Reduced boilerplate code
• Improved readability
• Fewer casting errors

• Better performance (single type check)

• Text Blocks

  Text blocks use triple-double quotes (""") to create multi-line string literals that preserve formatting and eliminate the need for escape sequences. Perfect for JSON, SQL, HTML, and other multi-line content.

String json = """
    {
      "name": "John Doe",
      "age": 30,
      "email": "john@example.com"
    }
    """;

String sql = """
    SELECT users.name, users.email, orders.total
    FROM users
    JOIN orders ON users.id = orders.user_id
    WHERE orders.status = 'completed'
    ORDER BY orders.total DESC
    """;

Benefits:

• Dramatically improved readability for multi-line strings
• No more escape sequence clutter
• Automatic indentation management

• Easier maintenance of embedded content

• Records

  Records provide a concise syntax for creating immutable data carrier classes. The compiler automatically generates constructors, accessors, equals(), hashCode(), and toString() methods.

// Traditional class: 40+ lines of boilerplate
public final class Person {
    private final String name;
    private final int age;
    // ... constructors, getters, equals, hashCode, toString
}

// Record: Just one line!
public record Person(String name, int age) {}

Benefits:

• Massive reduction in boilerplate code
• Immutability by default
• Perfect for DTOs and value objects

• Automatic implementation of common methods

• Enhanced Pseudo-Random Number Generators

  Java 17 introduces a new framework for random number generation with multiple high-quality algorithms, better stream support, and improved parallel processing capabilities.

// New flexible API
RandomGenerator rng = RandomGenerator.of("L64X128MixRandom");

// Excellent stream support
List<Integer> randomNumbers = rng.ints(100, 0, 100)
    .boxed()
    .collect(Collectors.toList());

// Multiple algorithm choices
RandomGenerator fast = RandomGenerator.of("Xoshiro256PlusPlus");
RandomGenerator quality = RandomGenerator.of("L128X256MixRandom");

Benefits:

• Multiple high-quality PRNG algorithms
• Better stream and parallel processing support
• Easy algorithm switching
• Improved performance

Why Upgrade to Java 17?

Long-Term Support

As an LTS release, Java 17 receives extended support, making it ideal for production applications that require stability and long-term maintenance.

Modern Language Features

The features in Java 17 represent years of evolution in the Java language, bringing it in line with modern programming paradigms while maintaining backward compatibility.

Improved Developer Productivity

Features like records, text blocks, and pattern matching significantly reduce boilerplate code, allowing developers to focus on business logic rather than ceremony.

Better Code Quality

Sealed classes and pattern matching enable more expressive, type-safe code with compile-time guarantees that catch errors early.

Migration Path

Java 17 maintains strong backward compatibility with previous versions. Most applications running on Java 11 (the previous LTS) can upgrade to Java 17 with minimal changes. The main considerations are:

1. Deprecated API Removals: Some deprecated APIs have been removed
2. Strong Encapsulation: Internal JDK APIs are more strictly encapsulated
3. Updated Dependencies: Ensure third-party libraries support Java 17

Conclusion

Java 17 is a significant milestone in Java’s evolution, combining stability as an LTS release with powerful new language features. Whether you’re building new applications or maintaining existing ones, Java 17 offers compelling reasons to upgrade:

• Sealed Classes for better domain modeling
• Pattern Matching for cleaner type checks
• Text Blocks for readable multi-line strings
• Records for concise data classes
• Enhanced Random Generators for flexible randomness

These features work together to make Java code more expressive, maintainable, and enjoyable to write. If you’re still on Java 11 or earlier, now is an excellent time to plan your migration to Java 17.