Difference between System.Properties and System.getenv

getenv is to get the environment changes of the system. For windows, the variables set in the system properties --> advanced --> environment variables will be displayed here (for linux, the variables set through export will be displayed here)
getProperties is to get the system Related attributes, including file encoding, operating system name, region, user name, etc., this attribute is generally obtained automatically by jvm and cannot be set.

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