JAVA JVM JRE JDK
https://stackoverflow.com/questions/11547458/what-is-the-difference-between-jvm-jdk-jre-openjdk
JVM是模仿计算机的java运行环境
http://www.geeksforgeeks.org/jvm-works-jvm-architecture/
JVM结构
It is mainly responsible for three activities.
- Loading
- Linking
- Initialization
JRE 包含了 JVM, 和一些类库(util等)不包含debugger, compiler等
The Java Runtime Environment (JRE) provides the libraries, the Java Virtual Machine, and other components to run applets and applications written in the Java programming language.
i.e. JRE = JVM + Java Packages Classes(like util, math, lang, awt,swing etc)+runtime libraries.
Java Runtime Environment contains JVM, class libraries, and other supporting files. It does not contain any development tools such as compiler, debugger, etc.
JDK 是 JRE的超集
The JDK is a superset of the JRE, and contains everything that is in the JRE, plus tools such as the compilers and debuggers necessary for developing applets and applications.
Java Developer Kit contains tools needed to develop the Java programs, and JRE to run the programs. The tools include compiler (javac.exe), Java application launcher (java.exe), Appletviewer, etc… Compiler converts java code into byte code. Java application launcher opens a JRE, loads the class, and invokes its main method. You need JDK, if at all you want to write your own programs, and to compile them. For running java programs, JRE is sufficient.