This blog post wrote in 2005. 2014.07 is modified, there are many incorrect links]
JDK is Java Development Kit, Java Development Kit. Learning Java programming requires downloading it, JDK lets us have a relatively complete toolbox, compile, debug and run the Java program. If we compile the program, debug it, give it to the customer, they obviously do not need JDK, they only need a platform that supports the Java program - JAVA runtime environment (JRE - JAVA RUNTIME Environment). Don't make a mistake when you download JDK.
The full name of JDK has changed multiple times. Sun's era is called The Java 2 SDK (J2SDK), now is Java Platform, Standard Edition Development Kit.
JDK version
JDK1.2 begins, Java Technical System / Java Platform (Java Platform) is divided into 3 directions, J2SE (or Java Standard Edition referred to as Java SE), J2EE, J2ME. Download Java SE when you begin a Java.
JDK is still in the continuous development, and its important versions are JDK1.2, JDK1.4 and JDK1.5.0 (ie JDK5.0), JDK6.0, JDK7.0, JDK8.0. In the link http://www.racle.com/technetwork/java/javase/downloads/index.html can download the latest JDK, as shown in the figure.
Select the appropriate version according to your machine and operating system. For example, your machine is 64-bit machine, the installed Windows operating system, √ After selecting Accept License Agreement, download JDK-8U5-Windows-x64.exe.
Now many people call JDK8.0 directly to Java 8. JDK 8 UPDATE 5 is referred to as JDK 8U5.
If you are interested in the history and code of JDK, you can check out J2SE Code Names.
Environment variable setting
After downloading and installing JDK, if you use Bluej as a development environment, you don't need to set the environment variable. If you use JDK, you can use Java Compiler (Java.exe), a Java Desk, Java.exe, a Mickey, a Java Desk, and a Java Compiler. Path (PATH) and ClassPath.
Open the Environment Variable window first. Take Windows 7 as an example: Control Panel \ System and Security \ System → Advanced System Settings → Environment Variables.
System Variable → New → Variable Name: Java_Home. Variables: C: \ Java \ JDK1.8.0_05 (follow your installation directory)
System Variables → New → Variable Name: ClassPath. Variable value:.;% Java_home% / lib (English "." Means the current path, the semicolon is a variety .jar's folder)
System Variables → Editing → Variable Name: Path, in the forefrunge of variable value plus:% java_home% / bin; (do not overwrite other content).
Now, open the black box through CMD, enter Java, you should see the interface below.
The main features of JDK version ("Programming Introduction (Java)")
Java was first released in January 1996 and was named Java Development Kit, abbreviated JDK JDK1.2 Full name: Perl style based on Java 2 Software Development Kit, abbreviated to Java 2 SDK or J2SDK.JDK1.4 introduced assertions (assert) [. Regular expression pattern matching mechanism, NIO] JDK 5 (J2se Development Kit 5.0) introduced 1. generic 2.For-Each loop 3. Autoboxing / Unboxing 4. Enumeration ( ENUMS) 5. Variable parameters (VARARGS) 6. Static imports Java.util.Concurrent JDK 6 No Language Changes WERE IntroducesD in Java Se 6.javase7 binary digital expressions use underscore to separate the numbers, such as 1_322_222 Switch statement supports string variable generic instances created TRY-WITH-RESOURCES statement simultaneously captures multiple exceptions Java 8Lambda Expressions (Method References, default methods) Improved Type Inference (Target Typing, Type Inference More
JDK often refers to Java Developer's Kit (or Java Development Kit), Sun Java 2 SDK (J2SDK) [see §2] on Sun's official website. JDK has a lot of versions.
J2se code names [http://java.sun.com/j2se/codenames.html]
Released Version: Version Name Chinese Name Release Date JDK 1.1.4 Sparkler Gems 1997-09-12 JDK 1.1.5 Pumpkin Pumpkin 1997-12-13 JDK 1.1.6 Abigail Abbeier - Women's name 1998-04 -24 JDK 1.1.7 Brutus Bruiti - Ancient Roman Politician and General 1998-09-28 JDK 1.1.8 Chelsea Chelsea - City Name 1999-04-08 J2SE 1.2 Playground Sports Field 1998-12-04 J2SE 1.2. 1 None None 1999-03-30 J2se 1.2.2 Cricket 蟋蟀 1999-07-08 J2SE 1.3 Kestrel Beauty Red Dragonfly 2000-05-08 J2se 1.3.1 Ladybird Ladybug 2001-05-17 J2SE 1.4.0 Merlin Gray Far 2002-02-13 J2SE 1.4.1 Grasshopper 蜢 2002-09-16 J2se 1.4.2 Mantis 螂 2003-06-26 J2SE 5.0 (1.5.0) Tiger Tiger 2004-9-29 will be released: J2SE 5.1 (1.5 .1) Dragonfly dragonfly merged to 6.0 J2SE 6.0 (1.6.0) Mustang Mustang Nouload J2SE 7.0 (1.7.0) Dolphin Dolphin
Starting from JDK1.2.2, the main versions are named by birds or mammals. And their revised version is named insects. In a forum, some people said: "JDK, a group of animals". Although there is a little bit of a little, it is more interesting and impressive than "a group of animals."
§1 JDK and JRE
Full Name Abbreviation Platform Name Javatm 2 Platform Standard Edition 5.0 J2SETM 5.0 Products Delivered Under The Platform J2setm Development Kit 5.0 JDKTM 5.0 J2SETM Runtime Environment 5.0 JRE 5.0
When you learn Windows programming, there is a SDK (Software Development Kit, which is a software development package). JDK lets us have a relatively complete toolbox, compile, debug and run the Java program. If we compile the program, debug it, give it to the customer, they obviously do not need JDK, they only need a platform that supports the Java program - Java runtime environment (JRE). [http://java.sun.com/j2se/overview.html]
Don't make a mistake when you download JDK. JRE plus the tools for compiling, debug the Java program, etc., is JDK.
J2SE Runtime Environment (JRE) and J2se Development Kit (JDK):
JRE provides Java APIS, Java Virtual Machine, and other components required to run Applets and Applications. It does not include the Java compiler, interpreter, etc. for development. JDK is a super-collection of JRE.
JDK includes the following seven main tools:
The Javac Java compiler converts the Java source code into bytecode.
Java Java interpreter, execute Java application byte code from class files directly.
AppletViewer Browser, a Java browser that performs Java applets on an HTML file.
Javadoc generates an HTML document according to Java source and instructions.
JDB Java debugger, you can perform programs, set breakpoints and check variables.
Javah generates a C proced to call the Java process, or build header files that can be called by the Java program.
JavaP Java reversible, displays accessible and data in the compiling class file, while displaying the meaning of byte code.
Sun offers free JDK, in JDK1.4.2, directly contains Java API source code, and JDK5.0 seems to be downloaded.
§2JAVA 2 platform and JDK5.0
JDK has been developing continuously. Among them, JDK1.2 has made significant improvements to earlier versions, so it is called Java 2 Platform (Java 2 platform). Although we are already using JDK1.5.0 (ie JDK5.0), we are still in the Java 2 platform. When is Java 3 Platform, you have to call the solar micro system.
The Java 2 platform is a collective, and it is not specific to (1.2) that version. According to the application area, Java 2 platform is divided into three types: J2SE, J2ME and J2EE. Since Sun launches Java, it will force it to make it out, so it constitutes a Sun One Net Environment system.
l J2se (Javatm 2Platform Standard Edition) is the standard version of Java2, mainly for desktop application programming; L J2ME (JavatM 2Platform Micro Edition) is primarily applied to embedded system development, such as mobile phones and PDA programming;
l J2EE (Javatm 2 Platform Enterprise Edition) JAVA2's Enterprise Edition is mainly used for distributed network programs.
Since the Java 2 platform consists of three different application directions, JDK is no longer referred to as Java Development Kit after introducing J2ME and J2EE, but refers to J2SETM Development Kit.
So JDK5.0 is J2SETM Development Kit 5.0.
About 5.0, We Have Changed The Version of this Release from 1.5.0 to 5.0 to better Reflect The Level of Maturity, Stability, Scalability and Security Built Into J2se. (TIGER ".). Http://java.sun.com/j2se/j2se-namechange.html
§3 JDK download and environment variable settings
1. Download and install JDK
Address: http://java.sun.com/j2se/1.4.2/download.html
The downloaded file is: J2SDK-1_4_2_04-Windows-i586-P.exe, run the execution installation directly.
JDK5.0 Download Address: Download JDK for WINDOWS
(Http://dlc.sun.com/jdk/jdk-1_5_0_01-windows-i586-p.exe) Direct operation is executed.
It is recommended to download the JDK Documentation at the same time.
2. Set an environment variable
Under the Windows 2000 or XP operating system, use the mouse to "My Computer" → Properties → Advanced → Environment Variables:
System Variable → New → Variable Name: Java_Home. Variable: C: /J2SDK1.4.1_05
System Variables → New → Variable Name: ClassPath. Variable value:.;% Java_home% / lib
System Variables → Editing → Variable Name: PATH, in the forefront of the variable value plus:% java_home% / bin; (do not overwrite other content)
(One English in Classpath "." After following a semicolon, indicating the current path's meaning)
Note: Setting the environment variable is a one-time knowledge, reference:
http://java.sun.com/j2se/1.5.0/install-windows.html
[I am from JDK1.4.2 upgrade, how to download and install JDK5.0 directly, I didn't try it. 】
