JDK -将java编译为字节码。由调试器，编译器等组成。

javac file.java // Is executed using JDK

JVM——执行字节代码。JVM使java平台独立。但是JVM因平台而异。

JRE - JVM与java运行时库一起执行java程序。

JVM是Java虚拟机-它实际上运行Java字节码。

JRE是Java运行时环境——其中包含JVM，并且是运行Java程序所需要的。

JDK是Java开发工具包——它是JRE，但添加了javac(这是编译Java源代码所需的工具)和其他编程工具。

OpenJDK是一个特定的JDK实现。

JVM

JVM (Java虚拟机)是一种抽象机器。它是一个提供运行时环境的规范，在该环境中可以执行java字节码。 jvm可用于许多硬件和软件平台。

JRE

JRE是Java运行时环境的首字母缩写。它用于提供运行时环境。它是JVM的实现。它是物理存在的。它包含一组库+ JVM在运行时使用的其他文件。

JDK

JDK是Java Development Kit的首字母缩写。它是物理存在的。它包含JRE +开发工具。

链接:- http://www.javatpoint.com/difference-between-jdk-jre-and-jvm

JRE执行应用程序，但JVM逐行读取指令，因此它是解释器。

JDK = JRE +开发工具

JRE = JVM +库类

JVM

The Java Virtual Machine (JVM) is the virtual machine that runs the Java bytecodes. The JVM doesn't understand Java source code; that's why you need compile your *.java files to obtain *.class files that contain the bytecodes understood by the JVM. It's also the entity that allows Java to be a "portable language" (write once, run anywhere). Indeed, there are specific implementations of the JVM for different systems (Windows, Linux, macOS, see the Wikipedia list), the aim is that with the same bytecodes they all give the same results.

JDK和JRE

要解释JDK和JRE之间的区别，最好是阅读Oracle文档并参考图:

Java Runtime Environment (JRE) 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. In addition, two key deployment technologies are part of the JRE: Java Plug-in, which enables applets to run in popular browsers; and Java Web Start, which deploys standalone applications over a network. It is also the foundation for the technologies in the Java 2 Platform, Enterprise Edition (J2EE) for enterprise software development and deployment. The JRE does not contain tools and utilities such as compilers or debuggers for developing applets and applications. Java Development Kit (JDK) 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.

注意，Oracle并不是唯一提供jdk的公司。

OpenJDK

OpenJDK是JDK的开源实现，也是Oracle JDK的基础。Oracle JDK和OpenJDK之间几乎没有区别。

区别在这个博客中说明:

Q: What is the difference between the source code found in the OpenJDK repository, and the code you use to build the Oracle JDK? A: It is very close - our build process for Oracle JDK releases builds on OpenJDK 7 by adding just a couple of pieces, like the deployment code, which includes Oracle's implementation of the Java Plugin and Java WebStart, as well as some closed source third party components like a graphics rasterizer, some open source third party components, like Rhino, and a few bits and pieces here and there, like additional documentation or third party fonts. Moving forward, our intent is to open source all pieces of the Oracle JDK except those that we consider commercial features such as JRockit Mission Control (not yet available in Oracle JDK), and replace encumbered third party components with open source alternatives to achieve closer parity between the code bases.

JDK 11的更新

Donald Smith的一篇文章试图消除Oracle JDK和Oracle的OpenJDK之间的差异:https://blogs.oracle.com/java-platform-group/oracle-jdk-releases-for-java-11-and-later

正如@Alan Evangelista在评论中提到的，Java Web Start已被Oracle在Java SE 9中弃用，并在Java SE 11中删除。

JVM:描述运行java程序的方式/资源的规范。实际执行字节代码，使java平台独立。在这个过程中，不同的平台是不同的。windows的JVM不能像UNIX的JVM那样工作。

JRE: JVM的实现。(JVM +运行时库)

JDK: JRE + java编译器等基本工具，从零开始构建java程序