如果需要运行java程序，只需安装JRE就可以了。
如果需要编写java程序，需要安装JDK。
JRE: (Java Runtime Environment). Covers most end-users needs. Contains everything required to run Java applications on your system.
JDK is a superset of JRE , and contains everything that is in JRE , plus tools such as the compilers and debuggers necessary for developing applets and applications. JRE provides the libraries, the Java Virtual Machine (JVM), and other components to run applets and applications written in the Java programming language.
1 Java SE Downloads
JavaSE是标准版 点击下载即可
JDK 13 Documentation
2 环境变量配置
cmd:
参考：
https://blog.csdn.net/qq_36667170/article/details/79323532