1-Initial knowledge of Java

Catalogue
• Java history
• Java Platform
• Java Development environment
• How Java works [simplified]

Java history

The history of Java is not recorded in detail, but it is marked by points of time and events.

Point in Time	Events
1991	Sun Company established Green Project. Oak's language was born.
1992	In September 1992, the Oak language, together with the green OS and some applications, was released on a small device called start 7. Sun opened a company called Firstperson, and the green Team was transferred to the company to develop a set-top box
1993	First person company relocated Oak. Turn to Web applications (background: WWW begins to sweep the world)
1994	Oak technology includes all source code for free public. Oak developed the Web browser Webrunner, and later renamed HotJava. The applet written by Oak makes the Web page move from static to dynamic
1995	When Oak was registered, it was found that the name was occupied and renamed Java. First person company dissolved.
1995-3-23	Java milestone, Java was named one of the top ten outstanding technology products. JDK1.0A2 version officially released
1996	Sun established JavaSoft branch to develop Java. Netscape supports Java. IBM, Symantec, inprise, Microsoft ie support java.
1997-2-19	JDK 1.1 (Java development Kit) released
1998-12-4	JDK 1.2 was released and the JDK was renamed J2SDK (Java 2 software development Kit). J2SDK 1.2 aka Java 2, and segment Java applications (J2ME, J2SE, ee)
2000-5-8	J2SDK 1.3 Released
2002-2-13	J2SDK 1.4 Released
2004-9-30	JDK 1.5 Released
2006-11-13	Sun at the JavaOne conference announced to Kaiyuan Java, and in the next more than a year, in succession, the various parts of the JDK under the GPL V2 agreement to open the source code, and the establishment of the OPENJDK organization to independent management of the source code.
2006-12-11	JDK 1.6 Released
2009-4-20	Oracle acquires Sun for $7.4 billion
2011-7-28	JDK 1.7 Released
2014-3-18	JDK 1.8 released

Java Platform

Platform	Description
Java Card	A platform that supports some small programs (Applets) running on small memory devices, such as smart cards.
Java ME (Micro Edition)	A platform that supports Java programs running on mobile devices (mobile phones, PDAs), streamlines Java APIs, and joins support for the Eastern Terminal, formerly known as J2ME.
Java SE (Standard Edition)	Supports the Java Platform for desktop applications and provides a complete Java Core API, formerly known as J2SE.
Java EE (Enterprise Edition)	The Java Platform for enterprise applications that support multi-tiered architectures, such as ERP and CRM applications, has been massively expanded (typically with javax.* as the package name) and related deployment support in addition to the Java SE API, which was previously known as a EE.

Java Development environment

• Java terminology

Term name	Abbreviations	explain
Java Development Kit	Jdk	Java Development Kit. The 1.2~1.4 version is known as the Java SDK, abbreviated J2SDK.
Java Runtime Environment	Jre	Java Run-time environment
Java 2	J2	An obsolete term used to describe the Java version between 1998-2006 years
Software Development Kit	Sdk	An obsolete term used to describe the JDK between 1998-2006
Update	U	Oracle Terminology for publishing modified bugs
NetBeans	——	Oracle's integrated development environment

• Java Technology System content

The JDK should contain the Java language, JRE, and Java development tools.
The JRE should contain the Java SE API and the Java Virtual machine.

• Building a Java development environment

1. Download and install the JDK
2. Configure Environment variables

Windows 7/8/8.1/10

Java_home= "JDK Installation path"
Path is added %JAVA_HOME%/bin .
Add in Classpath%JAVA_HOME%/lib/dt.jar;%JAVA_HOME%/lib/tools.jar

Linux

Modify ~/.bash_peofile (user) or/etc/profile (System), add
export JAVA_HOME=/usr/java/jdk1.8.0_101
export PATH=$JAVA_HOME/bin:$PATH
export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar

3.JDK Catalog

Catalogue	Description
Bin	Compilers and tools
Demo	Demonstrate
Docs	HTML-formatted class library document (unzip J2sdkversion-doc.zip)
Include	The file used to compile the local method
Jre	Java Runtime Environment file
Lib	Class library file
Src	After the class library source file (decompression src.zip)

How Java works [simplified]

instruction	Description
javac hello.java	The Java compiler hello.java compiles files into .class bytecode files
java hello	Invoking the JVM, the JVM of different platforms interprets bytecode files based on platform directives

References:

[History of 1].java
[2]. Zhou Zhiming. Deep understanding of Java Virtual Machines [M]. 2nd edition. Beijing: Mechanical industry Press, 2013.6.
[3]. Cay S.horstmann Gary Cornell.java Core Technology Volume I-Fundamentals [M]. 9th edition. Beauty, 2013.10

1-Initial knowledge of Java