DESCRIPTION
JDK (Java Development Kit) is a Sun Microsystems product for Java developers。Since its launch Java，JDK has become the most widely used Java SDK。JDK Java is the core of the whole，Including the Java Runtime Environment、Java tools and Java Foundation Classes。The first step is to learn the Java JDK。No JDK can not compile Java programs，If you only want to run Java programs，To ensure the appropriate JRE is installed。
Basic components included in the JDK
- Javac： translater，Convert source program to bytecode。
- jar：packaging tool，Package related class files into one file。
- javadoc：document generator，Extract documentation from source code comments。
- jdb：debugger，Troubleshooting tool。
- java：Run the compiled java program (.class suffix)。
- appletviewer：applet browser，A Java browser that executes Java applets on HTML files。
- javah：Generates a C procedure that can call a Java procedure，Or create a header file of a C procedure that can be called by a Java program。
- Javap：Java disassembler，Display accessible functions and data in compiled class files，Simultaneously display byte code meaning。
- jconsole: A Tool for System Debugging and Monitoring in Java。
Commonly used packages in JDK
- java.long： This is the base class of the system，For example, String, etc. are all here，This package is the only one that can be imported without(import)ready-to-use package。
- java.io: Here are all the classes related to input and output，such as file operations。
- java.nio;In order to complete the functions in the io package，A new package written to improve performance in the io package ，For example NIO non-blocking application。
- java.net: Here are the classes related to the network，e.g. URL，URLConnection, etc.。
- java.util: This is the system auxiliary class，Especially collection class Collection，List，Map etc.。
- java.sql: This is the class for database operations，Connection， Statement，ResultSet etc.。
- javax.servlet: This is JSP，Classes used by Servlet etc.。
JDK has different versions
- HE(J2SE)，standard edition，standard edition，is a version commonly used，Mainly used for desktop software programming，console development(JFC)。Since JDK 5.0，Renamed to Java SE。
- EE(J2EE)，enterprise edition，Enterprise Edition，Use this JDK to develop J2EE applications，Mainly used for website development and programming based on b/s mode。Since JDK 5.0，Renamed to Java EE。
- ME(J2ME)，micro edition，Primarily for mobile devices、java application development on embedded devices，Since JDK 5.0，Renamed to Java ME。
About Eclipse
Eclipse is an open source、Extensible development platform based on Java。in itself，It's just a framework and a set of services，Used to build a development environment through plug-in components。It mainly consists of Eclipse projects、Eclipse tool project and Eclipse technology project are composed of three projects，Specifically, it consists of four parts-Eclipse Platform、JDT、CDT and PDE。JDT supports Java development、CDT supports C development、PDE is used to support plug-in development，Eclipse Platformis an open and extensible IDE，Provides a common development platform。
Eclipse comes with a standard set of plugins，Includes Java Development Tools (Java Development Kit，JDK）。existEclipseIt is more convenient to write JAVA code and run the program on the platform，Eliminate the tedious steps of writing code in Notepad and then compiling and running it under DOS。
Original article written by LogStudio：R0uter's Blog » Java development environment Introduction
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