Windows 10 – Standard Value of PATH Variable

Your path is the concatenation of the system path followed by the user path. Additionally, system environment variables may not contain references to user environment variables, and any such references will not be expanded. To get the desired result, insert the reference to %JAVA_HOME% in the user environment variable PATH, or create such a variable if it doesn't already exist.

Perhaps a simplified example will make this clearer. Suppose the SYSTEM environment is

ProgramFiles = C:\Program Files
SystemRoot = C:\WINDOWS
PATH = %SystemRoot%\SYSTEM32

and the User JSmith's environment is

JAVA_HOME = %ProgramFiles%\Java\bin
USERPROFILE = C:\USERS\JSmith
PATH = %JAVA_HOME%\bin;%USERPROFILE%\bin

then the resulting path would be

C:\WINDOWS\SYSTEM32;C:\Program Files\Java\bin;C:\Users\JSmith\bin

as desired.

If you only need this to work for command prompt sessions, create a profile/init batch file and configure it in the registry, per https://stackoverflow.com/questions/17404165/how-to-run-a-command-on-command-prompt-startup-in-windows. E.g.,

reg add "HKCU\Software\Microsoft\Command Processor" /v AutoRun ^
  /t REG_EXPAND_SZ /d "%"USERPROFILE"%\init.cmd" /f

Then simply make modifications to the PATH in that batch file. E.g.,

SET USER_PATH=c:\whatever
SET PATH=%USER_PATH%;%PATH%