"In-depth understanding of Java Virtual Machines" Part I (Java technology system, Java Virtual machine, Java technology trends)

The first part goes into the Java1.java technology system

Sun's officially defined Java technology System includes several components:

• Java Program Set Language
• Java virtual machines on a variety of hardware platforms
• class file format
• Java API Class Library
• Third-party Java class libraries

JDK is the smallest environment to support Java program Development, Java programming language, Java Virtual machine, JAVAAPI class library collectively known as JDK
The JRE is a standard environment for Java programs to run, and the Javaseapi subset and Java virtual machines in the Javaapi class library are collectively known as the JRE

The Java technology system can be divided into 4 platforms according to the key business areas that Java technology focuses on:

• Java Card: Support for Java applets (Applets) running on small memory devices
• Java ME (Micro Edition): Support Mobile Terminal, formerly known as J2ME
• Java SE (Standard Edition): Supports desktop applications, providing the core of the complete Java Core API, formerly known as J2SE
• Java Edition: Enterprise applications that support multi-tiered architectures, formerly known as the Java EE

2.Java Virtual Machine

Three virtual machines currently commercially available are Oracle's hotspot VMS, IBM J9 VMS for JRockit VM,IBM, Inc.

The future of 3.Java technology

The development trend of Java technology
1) Modular
Jigsaw (Jigsaw) project in OSGi and Java9, the contention of modular specification
2) Mixed language
A growing number of Java Virtual machine-based languages, mixed language programming
Addressing specific domain issues through specific domain language is One Direction for current software development to respond to increasingly complex project requirements
From "Java language virtual machine" to "Multilingual virtual machine"
3) Multi-core parallel
The development direction of CPU hardware from high frequency to multi-core, the advent of multicore era, parallel programming more and more attention
4) further enrich the grammar
5) 64-bit virtual machine
With the further development of hardware, the computer will eventually be completely over to 64-bit, the mainstream of virtual machine applications will eventually from 32 to 64 bits
Enterprise-class applications often require more than 4GB of memory, and 64-bit virtual machines demand urgent
However, the current 64-bit virtual machines are lagging behind 32-bit VMS in terms of speed, with a large performance gap

From for notes (Wiz)

"In-depth understanding of Java Virtual Machines" Part I (Java technology system, Java Virtual machine, Java technology trends)