Introduction to some new features of Java 9

Accepted characteristics 1 Jigsaw project; Modular source code

Jigsaw project is to modularize java code and divide JRE into components that can cooperate with each other, which is also one of many features of Java 9. JEP is the first of four steps towards jigsaw. It will not change the real structure of JRE and JDK. JEP is to modularize JDK source code, so that the compiling system can compile modules and check module boundaries during construction. This project was originally released with Java 8, but due to the delay, it will be added to Java 9

Once it is complete, it may allow components to be customized according to a project's needs, thereby reducing the size of rt.jar. There are about 20000 classes in the rt.jar package of JDK 7 and JDK 8, but many classes are not used in some specific environments (even if some solutions are included in the compact distribution feature of Java 8, there is class redundancy). This is to make java easy to apply to small computing devices (such as network devices), improve its security and performance, and make it easier for developers to build and maintain these class libraries.

2. Simplify process API

Up to now, the ability of Java to control and manage system processes is limited. For example, in order to easily obtain the process PID of your program, you can either call the local program or use some workarounds yourself. More importantly, each platform needs a different implementation to ensure that you get the right results.

It is expected that the code can obtain Linux PIDs in the following way:

In Java 9, it can be changed as follows (all operating systems are supported):

This update will expand the interaction between Java and the operating system: add some new direct and clear methods to deal with PIDs, process names and states, and enumerate multiple JVMs and processes and more.

3. Lightweight JSON API

At present, there are many java tools for dealing with JSON, but the uniqueness of JSON API is that JSON API will be a part of Java language, lightweight and use the new features of Java 8. It will be placed in Java Util package (but JSON in JSR 353 is handled by a third-party package or other methods)

More about JSR 354

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More about JEP 143

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