Java/Java SE 10: What's New, Release History & Support Lifecycle

What Is New in Java 10

Java 10 is a feature release that introduced several key improvements focused on developer productivity, application performance, and the start of a new release cadence. The most significant changes include local-variable type inference, a consolidated garbage collection interface, and application class-data sharing.

What are the main language changes in Java 10?

The headline feature is JEP 286: Local-Variable Type Inference. This allows you to declare local variables using var instead of an explicit type, reducing boilerplate code while maintaining static typing. The compiler infers the type from the initializer expression.

// Before Java 10
ArrayList<String> list = new ArrayList<String>();
// With Java 10
var list = new ArrayList<String>();

In practice, this makes code less verbose, especially with complex generic types. It's strictly limited to local variables with initializers and cannot be used for method parameters or return types.

How did garbage collection improve?

Java 10 cleaned up the garbage collection architecture with two key JEPs. JEP 304 introduced a clean garbage collector interface, making it easier to add new GCs without touching the rest of the codebase. This is a foundational change for future GC development.

JEP 307 enabled parallel full garbage collection for the G1 garbage collector. Previously, G1's full GC used a single-threaded algorithm which could cause noticeable pauses. This change parallelizes that work, significantly reducing full GC pause times for G1 users.

What is Application Class-Data Sharing?

Application Class-Data Sharing (AppCDS) extends the original CDS feature to include application classes. It allows you to create a shared archive of pre-loaded classes that can be used by multiple JVM instances, reducing startup time and memory footprint.

This matters because it can lead to significant performance improvements for microservices and serverless environments where fast startup is critical. You create the archive once and then all JVMs on the same machine can benefit from it.

Were there any useful API additions?

Yes, a handy addition was the Optional.orElseThrow() method. This is a direct shortcut for Optional.get() but with a more descriptive name that clearly indicates it can throw an exception if no value is present.

// Before
String value = optionalValue.get();
// After
String value = optionalValue.orElseThrow();

Other API updates included full support for Unicode extensions in the Locale class and new methods for working with unmodifiable collections.