Java 16 Features

Author:
Java 16, released in March 2021, continues to enhance the Java platform with new features, performance improvements, and deprecations. This guide explores the key features introduced in Java 16, including pattern matching, records, and new stream methods. It also covers performance improvements, experimental features, and other changes in this release.

1. Pattern Matching for instanceof (Standard)

Java 16 introduced pattern matching for instanceof, a feature that simplifies the use of the instanceof operator and type casting. This enhancement allows developers to perform type checks and casts more concisely and safely. With pattern matching, the instanceof operator not only checks the type but also casts the variable to the desired type in a single step, reducing boilerplate code and potential errors.

Example

public class PatternMatchingExample {
    public static void main(String[] args) {
        Object obj = "Java 16";

        // Using pattern matching for instanceof
        if (obj instanceof String str) {
            System.out.println("Length: " + str.length());
        }
    }
}

Output:

Length: 7

Explanation

  • Simplified Casting: Pattern matching for instanceof eliminates the need for explicit casting, allowing you to declare a variable of the target type within the instanceof expression.
  • Improved Readability: By reducing boilerplate code, pattern matching for instanceof improves the readability and maintainability of Java applications.

2. Records (Standard)

Java Records, introduced in Java 14 as a preview feature and standardized in Java 16, provide a concise syntax for creating immutable data classes. Records are designed to reduce boilerplate code by automatically generating common methods such as constructors, getters, equals(), hashCode(), and toString(). They are particularly useful for modeling simple data-carrying classes with minimal code.

Key Features of Records

  1. Conciseness: Records automatically generate common methods, reducing boilerplate code.
  2. Immutability: Fields in a record are final and immutable by default.
  3. Automatic Implementations: Records automatically provide implementations for equals(), hashCode(), and toString() methods.
  4. Compact Syntax: Records use a compact syntax for defining data classes.

Basic Record Definition

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

Explanation

  • Concise Definition: The Person record is defined in a single line, specifying its components (name and age).
  • Immutability: The fields name and age are implicitly private and final.
  • Automatic Methods: The compiler automatically generates the constructor, getters, equals(), hashCode(), and toString() methods.

Example

public record Point(int x, int y) {
    // No need to implement equals(), hashCode(), or toString()
}

public class RecordsExample {
    public static void main(String[] args) {
        Point point = new Point(5, 10);
        System.out.println("Point: " + point);
    }
}

Output:

Point: Point[x=5, y=10]
Explanation
  • Concise Syntax: Records provide a concise syntax for defining data classes, automatically generating implementations for common methods.
  • Immutable Data: Records are implicitly final and provide immutable data, ensuring data integrity and reducing the risk of errors.

3. Migrate from Mercurial to Git + Migrate to GitHub

Java 16 marks the migration of the OpenJDK source code repositories from Mercurial to Git and from self-hosted servers to GitHub. This move aims to improve collaboration, streamline development processes, and take advantage of GitHub's features and tools.

4. Warnings for Value-Based Classes

What are Value-Based Classes?

Java 16 introduces warnings for value-based classes, which are classes designed to be immutable and have no observable identity. This feature helps developers adhere to best practices when using value-based classes and ensures proper usage.

Explanation

  • Best Practices: Warnings for value-based classes encourage developers to follow best practices, such as avoiding identity-based operations on these classes.
  • Code Quality: By highlighting potential issues, these warnings help improve the quality and maintainability of Java applications.

5. Strongly Encapsulate JDK Internals by Default

What is Strong Encapsulation?

Java 16 strengthens the encapsulation of JDK internals by default, restricting access to internal APIs. This change encourages developers to use standard APIs and improves the security and stability of Java applications.

Explanation

  • Encapsulation: Strong encapsulation restricts access to internal APIs, reducing the risk of unintended usage and improving application stability.
  • Standard APIs: By encouraging the use of standard APIs, this change enhances the compatibility and maintainability of Java applications.

6. New Stream Methods

Java 16 introduces new methods in the Stream class, enhancing its functionality and usability.

Stream.toList()

The Stream.toList() method collects the elements of a stream into an unmodifiable list. It provides a more convenient and readable alternative to Collectors.toList().

Example

import java.util.List;
import java.util.stream.Stream;

public class StreamToListExample {
    public static void main(String[] args) {
        List<String> list = Stream.of("a", "b", "c")
                                  .toList();

        System.out.println("List: " + list);
    }
}

Output:

List: [a, b, c]

Explanation

  • Unmodifiable List: The toList() method collects the elements of a stream into an unmodifiable list, providing a convenient and safe way to create lists from streams.
  • Readability: This method improves the readability and conciseness of code that collects stream elements into a list.

Stream.mapMulti()

The Stream.mapMulti() method allows for flat-mapping streams in a more flexible and efficient way. It provides an alternative to flatMap() with more control over how elements are mapped.

Example

import java.util.List;
import java.util.stream.Stream;

public class StreamMapMultiExample {
    public static void main(String[] args) {
        List<String> list = Stream.of("Java", "16")
                                  .<String>mapMulti((str, downstream) -> {
                                      for (char ch : str.toCharArray()) {
                                          downstream.accept(String.valueOf(ch));
                                      }
                                  })
                                  .toList();

        System.out.println("List: " + list);
    }
}

Output:

List: [J, a, v, a, 1, 6]

Explanation

  • Flexible Mapping: The mapMulti() method provides more flexibility in mapping stream elements, allowing for more complex transformations.
  • Efficiency: By providing control over how elements are mapped, this method improves the efficiency of flat-mapping operations.

7. Packaging Tool

The Packaging Tool, introduced as a standard feature in Java 16, allows developers to package Java applications into self-contained executables. This tool simplifies the deployment process and allows developers to distribute Java applications more easily.

Example

To package a Java application using the Packaging Tool, use the following command:

jpackage --input input-dir --name MyApp --main-class com.example.Main --main-jar myapp.jar

Explanation

  • Self-Contained Executables: The Packaging Tool allows developers to package Java applications into executables that include the JDK and application dependencies, simplifying deployment.
  • Cross-Platform: The Packaging Tool supports multiple platforms, allowing developers to distribute Java applications as native executables on Windows, macOS, and Linux.

8. Performance Improvements

ZGC: Concurrent Thread-Stack Processing

Java 16 improves the Z Garbage Collector (ZGC) with concurrent thread-stack processing, reducing pause times and improving performance for applications using ZGC.

  • Concurrent Processing: By processing thread stacks concurrently, ZGC reduces pause times and improves the overall performance and responsiveness of Java applications.
  • Performance: This improvement enhances the efficiency and scalability of applications using ZGC.

Concurrently Uncommit Memory in G1

Java 16 enhances the G1 garbage collector with the ability to concurrently uncommit memory, reducing memory usage and improving performance for applications using G1.

  • Memory Efficiency: By uncommitting memory concurrently, G1 reduces memory usage and improves the efficiency of memory management.
  • Performance: This feature enhances the performance and responsiveness of Java applications using G1.

Elastic Metaspace

Java 16 introduces elastic metaspace, which improves memory management by returning unused metaspace memory to the operating system more efficiently. This feature reduces memory footprint and improves performance.

  • Memory Management: Elastic metaspace returns unused memory to the operating system, reducing the memory footprint of Java applications.
  • Efficiency: This improvement enhances the efficiency and performance of memory management in Java applications.

Unix-Domain Socket Channels

Java 16 introduces Unix-domain socket channels, providing support for Unix-domain sockets in the java.nio.channels package. This feature enhances network communication and improves performance for applications running on Unix-based systems.

  • Unix-Domain Sockets: Unix-domain socket channels provide support for Unix-domain sockets, improving the performance and efficiency of network communication on Unix-based systems.
  • Network Communication: This feature enhances the capabilities of the java.nio.channels package, providing more options for network communication.

9. Experimental, Preview, and Incubator Features

Sealed Classes (Second Preview)

Sealed classes, reintroduced as a preview feature in Java 16, allow you to restrict which classes can be extended or implemented. This feature enhances encapsulation and provides more control over class hierarchies.

Example

public sealed class Shape permits Circle, Square {
}

public final class Circle extends Shape {
}

public final class Square extends Shape {
}

Explanation

  • Class Hierarchy Control: Sealed classes restrict which classes can extend or implement them, providing more control over class hierarchies and improving encapsulation.
  • Encapsulation: By limiting the inheritance of sealed classes, this feature enhances encapsulation and reduces the risk of unauthorized modifications.

Vector API (Incubator)

The Vector API, introduced as an incubator feature in Java 16, provides a way to perform vector computations in Java. This API enhances performance for applications that require mathematical and scientific computations.

  • Vector Computations: The Vector API provides a set of classes and methods for performing vector computations, improving the performance and efficiency of mathematical and scientific applications.
  • Performance: By leveraging vectorized operations, this API enhances the performance of applications that require intensive computations.

Foreign Linker API (Incubator) + Foreign-Memory Access API (Third Incubator)

The Foreign Linker API and the Foreign-Memory Access API, introduced as incubator features in Java 16, provide a way to interact with native code and memory. These APIs allow developers to work with native libraries and memory more efficiently and safely.

  • Native Interactions: The Foreign Linker API provides a way to call native functions from Java, while the Foreign-Memory Access API allows access to native memory outside of the Java heap.
  • Efficiency and Safety: These APIs improve the efficiency and safety of working with native code and memory, reducing the risk of errors and improving performance.

10. Deprecations

Terminally Deprecated ThreadGroup stop, destroy, isDestroyed, setDaemon, and isDaemon

Java 16 terminally deprecates several methods in the ThreadGroup class, including stop, destroy, isDestroyed, setDaemon, and isDaemon. These methods are marked for future removal due to their limited use and potential for causing issues.

11. Other Changes in Java 16

Add InvocationHandler::invokeDefault Method for Proxy's Default Method Support

Java 16 introduces the InvocationHandler::invokeDefault method, which allows default methods in interfaces to be invoked through dynamic proxies. This feature enhances the capabilities of dynamic proxies and improves their usability.

  • Default Methods: The invokeDefault method allows default methods in interfaces to be invoked through dynamic proxies, providing more flexibility and control over proxy behavior.
  • Usability: By supporting default methods, this feature enhances the usability and functionality of dynamic proxies in Java applications.

Day Period Support Added to java.time Formats

Java 16 adds day-period support to the java.time package, allowing for the formatting and parsing of day periods (such as "AM" and "PM") in date and time formats. This feature improves the flexibility and usability of date and time formatting.

  • Day Periods: Day period support allows for the inclusion of day periods in date and time formats, enhancing the flexibility and accuracy of date and time handling in Java applications.
  • Formatting and Parsing: This feature improves the usability of the java.time package by providing more options for formatting and parsing date and time values.

Alpine Linux Port

Java 16 introduces a port for Alpine Linux, a lightweight Linux distribution commonly used in container environments. This port enhances the compatibility and performance of Java applications running in containerized environments.

  • Container Environments: The Alpine Linux port improves the compatibility and performance of Java applications running in container environments, providing a lightweight and efficient runtime.
  • Compatibility: By supporting Alpine Linux, Java 16 enhances the flexibility and usability of the Java platform in modern deployment environments.

Windows/AArch64 Port

Java 16 introduces a port for Windows/AArch64, providing support for Java applications running on Windows systems with ARM-based processors. This port enhances the compatibility and performance of Java applications on ARM-based hardware.

  • ARM-Based Hardware: The Windows/AArch64 port provides support for Java applications running on ARM-based processors, improving compatibility and performance on modern hardware.
  • Flexibility: By supporting Windows/AArch64, Java 16 enhances the flexibility and usability of the Java platform across a wider range of devices and environments.

Enable C++14 Language Features

What are C++14 Language Features?

Java 16 enables the use of C++14 language features in the JDK codebase, improving the maintainability and performance of the JDK. This change allows developers to take advantage of modern C++ features when contributing to the JDK.

  • Modern C++: Enabling C++14 language features improves the maintainability and performance of the JDK by allowing developers to use modern C++ features and idioms.
  • JDK Development: This change enhances the development process for the JDK, making it easier to maintain and improve the codebase.

Conclusion

Java 16 introduces several key features and improvements, including pattern matching for instanceof, records, and new stream methods. These features enhance developer productivity, application performance, and the flexibility of the Java platform. By understanding and leveraging these features, developers can build more efficient and maintainable Java applications.

For a complete list of all changes in Java 16, refer to the official Java 16 release notes.

Series: Java Release-wise New Features

Comments

Post a Comment

Leave Comment