Java Development Kit 10 introduced several significant enhancements aimed at improving developer productivity and JVM performance.

Local Variable Type Inference

One of the most visible changes is the introduction of local variable type inference. This feature allows the compiler to deduce the type of a local variable from its initializer. By utilizing the var identifier, developers can omit explicit type declarations, reducing boilerplate code without sacrificing static type safety.

Implementation Example

var dataBuffer = new java.util.LinkedList<Double>();
var processor = dataBuffer.stream();

This syntax is particularly useful when dealing with generic types where the declaration becomes verbose. It also streamlines iteration logic:

for (var entry : dataBuffer) {
    System.out.println(entry);
}

Application Class-Data Sharing

To optimize startup latency and memory footprint, JDK 10 expanded Class-Data Sharing (CDS) to include application classes. Previously, CDS was limited to core JDK classes. This extension allows archives to contain classes from the application class path, which is beneficial for containerized environments and microservices where rapid scaling is required.

Configuration Steps

1. Generate Archive: Dump the class data upon JVM exit.

   java -XX:ArchiveClassesAtExit=app_cds.jsa -cp application.jar
   

2. Utilize Archive: Load the shared data during subsequent startups.

   java -XX:SharedArchiveFile=app_cds.jsa -cp application.jar
   

This mechanism reduces the time spent loading and verifying classes during initialization.

Unified Garbage Collection Interface

Internal JVM architecture received updates through a unified interface for garbage collectors. This refactor improves the maintainability of the JVM codebase by standardizing how different GC algorithms interact with the virtual machine. While this change is primarily internal, it facilitates easier integration of new garbage collection strategies and experimental features.

Conceptual Implementation

Developers extending GC logic would interact with a standardized contract.

public class CustomMemoryManager implements GarbageCollectorInterface {
    public void executeCollection() {
        // Custom memory reclamation logic
    }
}

This modularity supports the development of specialized collectors tailored for specific workload requirements without modifying core JVM structures.