#3 Features and Enhancements in Java 17

#3 Features and Enhancements in Java 17

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Java 17, released in September 2021, marks another significant milestone in the evolution of the Java programming language. As a Long-Term Support (LTS) release, Java 17 brings a range of new features and enhancements that improve the language’s performance, security, and developer productivity. Here, we delve into the key features and enhancements introduced in Java 17.

1. Sealed Classes

Sealed classes and interfaces restrict which other classes or interfaces can extend or implement them. This feature enhances the control over the class hierarchy and allows for more predictable and secure code.

Example:

public abstract sealed class Shape 
    permits Circle, Square, Rectangle {}

public final class Circle extends Shape {}
public final class Square extends Shape {}
public final class Rectangle extends Shape {}

2. Pattern Matching for switch (Preview)

Pattern matching for switch expressions and statements simplifies complex data-oriented queries by extending pattern matching to switch statements. This feature allows for more concise and readable code.

Example:

static String formatShape(Shape shape) {
    return switch (shape) {
        case Circle c -> "Circle with radius " + c.radius();
        case Rectangle r -> "Rectangle with area " + (r.length() * r.width());
        case Square s -> "Square with side " + s.side();
        default -> "Unknown shape";
    };
}

3. New java.util.random Interface

Java 17 introduces a new interface, java.util.random.RandomGenerator, which provides a common API for all random number generators. This enhancement aims to improve the flexibility and extensibility of random number generation.

Example:

RandomGenerator randomGenerator = RandomGenerator.of("L64X128MixRandom");
int randomInt = randomGenerator.nextInt();

4. Enhanced Pseudorandom Number Generators (PRNGs)

In addition to the new interface, Java 17 includes new implementations of pseudorandom number generators, such as LXM, Xoshiro/Xoroshiro, and more. These provide better performance and higher-quality random numbers.

Example:

RandomGenerator generator = RandomGeneratorFactory.of("L64X128MixRandom").create();
long randomLong = generator.nextLong();

5. Strong Encapsulation of JDK Internals

Java 17 strengthens the encapsulation of internal APIs, making it harder to access non-public elements of the JDK. This change enhances the security and maintainability of Java applications.

6. Context-Specific Deserialization Filters

Deserialization filters introduced in Java 17 allow developers to specify context-specific filters that can control the deserialization process, improving security and preventing attacks through unsafe deserialization.

Example:

ObjectInputFilter filter = info -> {
    if (info.serialClass() == null) return ObjectInputFilter.Status.UNDECIDED;
    if (info.serialClass() == SomeClass.class) return ObjectInputFilter.Status.ALLOWED;
    return ObjectInputFilter.Status.REJECTED;
};
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("data.obj"));
ois.setObjectInputFilter(filter);

7. Foreign Function & Memory API (Incubator)

This API provides a more efficient way to interact with native code and memory outside the JVM, reducing the need for JNI (Java Native Interface). It is still in the incubation phase but offers a glimpse into future capabilities for high-performance computing.

Example:

try (MemorySegment segment = MemorySegment.allocateNative(100)) {
    MemoryAccess.setIntAtOffset(segment, 0, 42);
    int value = MemoryAccess.getIntAtOffset(segment, 0);
}

8. Deprecation of the Applet API for Removal

Java 17 marks the beginning of the end for the Applet API by deprecating it for future removal. This reflects the declining use and support of applets in modern web applications.

9. Enhanced Pipelining in G1 Garbage Collector

The G1 garbage collector sees improved performance with enhancements that include better parallelism and improved memory management. These changes result in reduced pause times and better overall performance.

10. Other Enhancements and Deprecations

Java 17 also includes various smaller enhancements and deprecations:

  • Removal of the experimental AOT and JIT compiler.
  • Improved performance for java.nio.channels and java.nio.file classes.
  • Various enhancements to the Java Flight Recorder and the Java Management Extensions (JMX).

11. Record Classes

Java 17 introduced the concept of record classes, a new type of class that is intended to be a transparent carrier for immutable data. This feature simplifies the creation of classes that are primarily used to store data by automatically generating common methods such as equals(), hashCode(), and toString(). Record classes provide a concise syntax for declaring such data-carrying classes.

Key Features of Record Classes
  1. Immutable Data: Record classes are immutable by design. All fields are final and private.
  2. Automatic Generation of Methods: The compiler automatically generates the following methods:
    • equals(Object obj)
    • hashCode()
    • toString()
    • Accessor methods for all fields (e.g., name() for a field named name)
  3. Concise Syntax: Record classes reduce boilerplate code, making the code more readable and maintainable.
Defining a Record Class

A record class is defined using the record keyword, followed by the class name and a list of components (fields) in the header.

Example:

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

This single line of code generates:

  • A class Person with final fields name and age.
  • A constructor that takes name and age as parameters.
  • Getter methods name() and age().
  • equals(), hashCode(), and toString() methods.
Using Record Classes

Record classes are used just like any other class, but with less boilerplate.

Example:

public class Main {
    public static void main(String[] args) {
        Person person = new Person("Alice", 30);
        System.out.println(person.name()); // Output: Alice
        System.out.println(person.age());  // Output: 30
        System.out.println(person);        // Output: Person[name=Alice, age=30]
    }
}

Conclusion

Java 17 builds on the strengths of its predecessors, introducing features that enhance developer productivity, security, and performance. As a Long-Term Support release, it offers a stable and reliable platform for developing modern Java applications. By incorporating sealed classes, enhanced pattern matching, new random number generators, and improved garbage collection, Java 17 continues to maintain its relevance and appeal in the rapidly evolving landscape of software development.

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