What is New in Java 17

Java 17 is a significant release as it is the latest Long-Term Support (LTS) version after Java 11. Released in September 2021, Java 17 brings several exciting features and enhancements aimed at improving productivity, performance, and security for developers. Here’s an overview of its new features, complete with definitions, examples, and remarks to help you understand its significance.

1. Sealed Classes

Definition:

Sealed classes allow you to restrict which classes can extend or implement a given class or interface. This provides better control over the class hierarchy and ensures that future changes don’t accidentally break the intended design.

Syntax:

public sealed class Shape permits Circle, Rectangle {
    // class content
}

public final class Circle extends Shape {
    // class content
}

public final class Rectangle extends Shape {
    // class content
}

Remarks:

Sealed classes are particularly useful in domain-driven designs where the model hierarchy must be well-defined. By explicitly specifying permitted subclasses, you ensure the integrity of your model.

2. Pattern Matching for Switch (Preview)

Definition:

This enhancement extends the switch statement to allow pattern matching, simplifying the code by combining the matching and extraction logic.

Example:

Object obj = 123;
String result = switch (obj) {
    case Integer i -> "Integer: " + i;
    case String s -> "String: " + s;
    default -> "Unknown type";
};

Remarks:

Pattern matching for switch makes the code more readable and concise, especially when working with complex types. This feature is still in preview, so its final behavior might evolve in future versions.

3. New JDK Packaging Tool (jpackage)

Definition:

jpackage is a command-line tool introduced to simplify the creation of platform-specific packages for Java applications.

Example:

jpackage --input input-dir --name MyApp --main-jar app.jar --type dmg

Remarks:

jpackage is a welcome addition for developers needing native installers for their Java applications. It eliminates the need for third-party tools and integrates seamlessly with the JDK.

4. Enhanced Pseudorandom Number Generators

Definition:

Java 17 introduces new interfaces and implementations for pseudorandom number generators (PRNGs), making it easier to use custom or non-linear algorithms.

Example:

RandomGenerator generator = RandomGenerator.of("L64X128MixRandom");
System.out.println(generator.nextInt());

Remarks:

This enhancement provides better performance and flexibility for applications requiring advanced random number generation.

5. Deprecations and Removals

Definition:

Several old or obsolete features were removed or deprecated, such as:

• Removal of the Applet API.
• Deprecation of RMI Activation.

Remarks:

Cleaning up the JDK improves maintainability and removes outdated features that are no longer widely used, paving the way for modern development.

6. Foreign Function and Memory API (Incubator)

Definition:

This API provides a way to call native libraries and manage off-heap memory safely and efficiently.

Example:

try (MemorySegment segment = MemorySegment.allocateNative(1024)) {
    segment.set(ValueLayout.JAVA_INT, 0, 42);
    System.out.println(segment.get(ValueLayout.JAVA_INT, 0));
}

Remarks:

This API is still in the incubation phase, but it’s a promising addition for applications that need high-performance native interop capabilities.

7. Improved Security Features

Highlights:

• Strong encapsulation of JDK internals.
• New macOS notarization requirements supported by default.
• Updates to TLS implementations.

Remarks:

Java 17 enhances the security posture of applications by default, aligning with modern security practices.

Why Upgrade to Java 17?

Java 17 brings modern features and tools that enhance developer productivity and application performance. As an LTS release, it offers long-term stability, making it an excellent choice for enterprises and individual developers looking to modernize their Java projects.