This project provides a set of Java code examples illustrating the new language features and APIs introduced in Java 9.

The examples are implemented as a set of easy to run tests, using JUnit (5 and AssertJ).

It's fair to say that there aren't any big new language features for developers to get excited about in Java 9, as there were in Java 8 (such as the Stream API and Lambdas). The Java Platform Module System (JPMS) is by far the biggest new feature in Java 9, affecting the platform libraries, the language and the runtime. However, beyond JPMS, performance improvements, and the new REPL, there are also a number of smaller, new language features introduced in Java 9 that are still worth Java programmers familiarising themselves with. A list of these less well publicised language features is provided below. The ones highlighted (in bold) are those for which code examples are provided in this project.

• Factory methods for Collections
• Private methods in interfaces
• java.util.Optional enhancements
• Stream API enhancements
• Reactive Streams API standard implementation
• Process API enhancements
• CompletableFuture enhancements
• Effectively final variables in try-with-resources blocks
• UTF-8 Property files
• Support for the Unicode 7 and 8 standard

The source code for the examples can be found in the src/test/java folder.

An explanation and guidance on the usage on each of the showcased language features can be found in the Javadoc of each of the code examples. (See commands for generating Javadoc below).

You will need to install a Java 9 JDK.

Support is provided for building and running the project using either Gradle (see build.gradle) or Maven (see pom.xml). For Gradle, the minimum required version of Gradle will be installed if you use ./gradlew. For Maven, ensure you install a version which supports Java 9. The project has been tested to work using Maven 3.5.3+.

To compile and run all the example tests, enter the following command in the project's root folder:

./gradlew clean test

To generate the Javadoc use, the following command:

./gradlew clean javadocTests

The generated Javadoc can be found in the standard location for a Gradle project - build/docs/javadoc/index.html. This provides an example of the updated Javadoc generated in Java 9, which uses HTML5 and supports searching.

To compile and run all the example tests, enter the following command in the project's root folder:

mvn clean test

To generate the Javadoc, use the following command:

mvn javadoc:test-javadoc

The generated Javadoc can be found in the standard location for a Maven project - target/site/testapidocs/index.html.

You can find similar code examples for the new features introduced in earlier Java versions (e.g. 7 and 8) in my Bitbucket projects at https://bitbucket.org/neilbrown/