System properties are set on the Java command line using the -Dpropertyname=value syntax. They can also be added at runtime using System.setProperty(String key, String value) or via the various System.getProperties().load() methods. To get a specific system property you can use System.getProperty(String key) or System.getProperty(String key, String def). Environment variables are set in the OS, e.g. in Linux export HOME=/Users/myusername or on Windows SET WINDIR=C:\Windows etc, and, unlike properties, may not be set at runtime. To get a specific environment variable you can use System.getenv(String name).

我认为两者之间的区别归结为获取途径。环境变量可以被任何进程访问，而Java系统属性只能被添加它们的进程访问。

同样，正如波西米亚所说，env变量是在操作系统中设置的(然而，它们“可以”通过Java设置)，系统属性是作为命令行选项传递或通过setProperty()设置的。