The relationship and differences between JDK and JRE

Source: Internet
Author: User
Jdk:java Development Kit Java Development Toolset, which contains:
JRE (Java Runtime Environment), a collection of environments necessary to run Java programs, including the JVM standard implementation and the Java Core Class library.
Java ToolPak, Tool Library contains seven main programs:
Javac:java compiler to convert Java source code into bytecode.
The Java:java interpreter executes the Java application byte code directly from the class file.
Appletviewer: Applet browser, a Java browser that executes Java applets on HTML files.
Javadoc: Generates HTML documents According to Java source code and description statements.
Jdb:java debugger, you can execute the program line by row, set breakpoints and check variables.
Javah: Generates a C procedure that can invoke a Java procedure, or a header file that can be called by a Java program.
The Javap:java disassembler, which displays the accessible functionality and data in the compiled class file, shows the meaning of the byte code.
Java's base Class library (Rt.jar)

There are three versions of the JDK:
J2se:standard Edition, Standard Edition, is a version we usually use.
J2ee:enterpsise edtion, Enterprise Edition, using this JDK to develop the Java EE application

J2me:micro Edtion, a Java Application Java development tool (JDK) used primarily for mobile devices and embedded devices, is the first development environment used by many Java experts.


Running a Java program requires only the JRE, but to develop a Java program, you need to download the JDK, and remember that the JDK already contains the JRE. If the downloaded JDK is an. exe executable file, install it directly, so that our computer has the JDK development and running environment, if the downloaded JDK is a compressed package, after decompression is a folder, then we need to configure the JDK environment variable. Specific configuration to refer to the online tutorial, I am too lazy to copy.

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