Oracle Java Day 2017

Log of study session participation.

Java 9

Java 9 Features
Module System	jigsaw,Suitable for Cloud deployment, Docker, module-info.Defined in java
The Modular JDK
jShell
Encapsulate Internal APIs
jlink	tool, Linker can produce custom runtime image(Regular, JVM specific memory images, fast exec)
Ahead of Time (AOT) Compilation	statically compile java classes,Static and dynamic compilation integration
G1 Garbage Collector as the Default	Divide the heap space into fixed sizes, E, S,Mark O

Modularization method

module com.foo.bar{
  require com.foo.bar
  exports com.foo.bar
}

Modular Development

Modularization is possible in each layer
Modular Application
Modular Link
Modular JDK

Accessibility	Java 9 Accessibility
public	public to everyone
	public but only ...
	public only within a module
protected	protected

private	private

src/module-info.java

module hello.world{

exports com.example.hello; // Externally published packages requires java.base; }

hello.world
com.example.hello public
(No concealed packages)hiding

Module-info.class is added to the jar, access is restricted by this class
Can be imported in module units (not class units) -> Reduced file size to deploy
An error will occur if there is no module at startup Circular dependencies can also be detected

Migrating from the top down

Third-party library dependencies -> Extract dependencies with the jdeps command
Automatic Modules Auto-modular (when you want to use a third-party lib for modularization) JAR file name is module name Publish everything
```
    module hello.world{
      exports com.example.hello to myapp;
```

requires java.base; // added by default requires jackson-core; opens com.myapp.domain to jackson.databind // Behavior only when using reflection

        uses javax.print.PrintServiceLookup
      }

      module printlib{
        provides javax.print.PrintServiceLookup with groovy.backend.CodeEvaluatetionEngineFactory;
      }

JDK layout assumptions Directory change, rt.jar
Class loader assumptions Class load order
System property changes
Reference material JEP 261

Avoiding module circular dependencies

Dependency diagram

httpClient.java (depends on logging.api) | > loging.apis interface LogSPI < | logging.impl (depends on logging.api) class HTTPLogger implements LogSPI

The future of Java

Java Future	The future of Java
uniform model	object, Array, value, types, methods
post-threaded	Confined/immutable data
Data Layout	Codes like a class, works like an int!

Data Layout

class Point {
  final int x;
  final int y;
}

 Point[] pts = |x|y|x|y|x|y|I want to make it an image of

now,|x|y| |x|y| |x|y|Image with a gap like Less efficient with GC

Java EE 8

Java EE 8
JAX-RX2.1
Servlet 4.0	HTTP/2 performance, server push
JSON-B 1.0	JSON <-> Java binding
JSON-P 1.1
CDI 2.0
Bean Validation
JSF 2.3
Security 1.0

Deep Learning

deepleaning4j