What are the features introduced in Java 9?

Table of Contents

• Introduction
• Key Features of Java 9
  • 1. Java Platform Module System (JPMS)
  • 2. Enhanced Stream API
  • 3. New Optional Methods
  • 4. Multi-Release JAR Files
  • 5. JShell: The Java Shell
  • 6. Improved Javadoc
  • 7. Reactive Streams
• Conclusion

Introduction

Java 9 brought significant enhancements and new features that improved performance, modularity, and developer productivity. One of the most notable changes was the introduction of the Java Platform Module System (JPMS), which allows for better organization of code into modules. This guide covers the key features of Java 9 and their implications for developers.

Key Features of Java 9

1. Java Platform Module System (JPMS)

The JPMS, also known as the Jigsaw project, allows developers to create modular applications. This feature helps in encapsulating code, reducing dependencies, and improving security.

• Benefits:
  • Improved Maintainability: Modules can be developed and maintained independently.
  • Strong Encapsulation: Only the specified packages are accessible outside the module.
  • Better Performance: The JVM can optimize the performance of modular applications.

2. Enhanced Stream API

Java 9 introduced several improvements to the Stream API, making it easier to work with streams of data.

• New Methods:
  • takeWhile(Predicate<T> predicate): Returns a stream that takes elements while the predicate is true.
  • dropWhile(Predicate<T> predicate): Skips elements while the predicate is true.
  • ofNullable(T t): Creates a stream from a value that may be null.

Example:

3. New Optional Methods

Java 9 added new methods to the Optional class to enhance its functionality.

• New Methods:
  • ifPresentOrElse(Consumer<? super T> action, Runnable emptyAction): Executes an action if a value is present, or runs an empty action if not.
  • or(Supplier<? extends Optional<? extends T>> supplier): Returns the current optional if present, otherwise returns the supplied optional.

Example:

4. Multi-Release JAR Files

Java 9 allows developers to create multi-release JAR files that can contain versions of classes for different Java versions. This feature facilitates backward compatibility and version-specific optimizations.

• Benefits:
  • Easier Library Management: Libraries can provide different implementations based on the Java version.
  • Seamless Upgrades: Developers can upgrade libraries without breaking older Java applications.

5. JShell: The Java Shell

Java 9 introduced JShell, an interactive command-line tool for evaluating Java expressions, statements, and programs. It provides a REPL (Read-Eval-Print Loop) experience.

• Benefits:
  • Faster Prototyping: Quickly test snippets of code without creating a full project.
  • Learning Tool: Ideal for beginners to learn Java syntax and features interactively.

6. Improved Javadoc

Javadoc received significant enhancements in Java 9, including the ability to generate HTML5-compliant documentation. This makes the generated documentation more readable and modern.

• New Features:
  • Search Functionality: Enhanced search capabilities within the generated documentation.
  • Summary Lists: Improved summary lists for packages, classes, and methods.

7. Reactive Streams

Java 9 introduced a new java.util.concurrent.Flow API that supports the reactive programming paradigm, making it easier to handle asynchronous data streams.

• Components:
  • Publisher: Produces a stream of data.
  • Subscriber: Consumes data from the publisher.
  • Processor: A combination of both publisher and subscriber.

Conclusion

Java 9 introduced a variety of features aimed at improving modularity, enhancing existing APIs, and providing new tools for developers. The Java Platform Module System (JPMS) is particularly noteworthy for enabling better code organization and maintainability. Other enhancements, such as the improved Stream API, JShell, and multi-release JARs, contribute to a more productive and efficient development experience. Understanding these features can help developers leverage the full potential of Java 9 in their applications.