In-depth understanding of Java Virtual Machines Note 01: Approaching Java

1.1 Java's technical system

Sun's official definition of the Java technology system consists of the following components:

• Java programming language
• Java virtual machines on a variety of hardware platforms
• class file format
• Java API Class Library
• Third-party Java class libraries from business and open source communities

Java programming language, Java Virtual machine, Java API Class library are collectively referred to as JDK (Java development Kit), JDK is the smallest environment for Java program Development

1.2 Java Technology System

1. Java Card: A platform that supports some Java applets (Applets) running on small memory devices, such as smart cards.
2. Java ME (Micro Edition): This version was formerly known as J2ME. Java ME provides a robust and flexible environment for applications running on mobile devices and embedded devices such as mobile phones, PDAs, TV set-top boxes, and printers. Java ME includes a flexible user interface, robust security model, many built-in network protocols, and rich support for Web and offline applications that can be dynamically downloaded. Applications based on the Java ME specification need to be written once, can be used for many devices, and can take advantage of the native capabilities of each device.
3. Java SE (Standard Edition): Java SE was formerly known as J2SE. It allows you to develop and deploy Java applications that are used in desktops, servers, embedded environments, and live environments. Java SE contains classes that support the development of Java WEB Services, providing the basis for Java platform,enterprise Edition (Java EE).
4. Java EE (Enterprise Edition): This version was formerly known as the EE. The Enterprise Edition helps develop and deploy portable, robust, scalable, and secure server-side Java applications. Built on the Java SE, Java EE provides Web services, component models, management, and communication APIs that can be used to implement enterprise-class service-oriented architecture (service-oriented Architecture,soa) and Web 2.0 applications.

1.3 Java History

• April 1991: Java predecessor Oak
• May 1995 23: Renaming Java, releasing Java1.0
• January 23, 1996: JDK1.0 released, offering Sun Class VMS
• April 1996: First Java One conference
• February 19, 1997: Sun releases JDK1.1
• 199912 Month 4th: JDK1.2, split 3 directions, J2M3, J2SE, Java EE
• April 27, 1999: Hotspot Virtual Machine released
• May 8, 2000: JDK1.3 released
• February 13, 2002: JDK1.4 released, (2002 Microsoft. Net Framework Release)
• September 30, 2004: JDK1.5 released
• December 11, 2006: JDK1.6 released, enabling Java SE6, Java EE 6, Java ME6
• November 13, 2006: JavaOne conference, Sun announces Java Open Source, establishes OPENJDK organization to manage open source code
• February 19, 2009: JDK1.7 completes the first milestone version
• On April 20, 2009, Oracle Corporation acquired Sun Corporation for $7.4 billion and the Java trademark was owned by Oracle.
• July 2011: JDK1.7 Released
• March 19, 2014: JDK1.8 released
• 2017: JDK1.9 will be released

1.4 Java Virtual Machine history

1. Sun Classic/exact VMS
2. Sun HotSpot VMS
3. Sun mobile-embedded vm/meta-circular VM
4. BEA JROCKIT/IBM J9 VM
5. Azul Vm/bea Liquid VM
6. Apache harmony/google Android Dalvik VM
7. Microsoft JVM and other

In-depth understanding of Java Virtual Machines Note 01: Approaching Java