no JAVA_HOME in the path

[Amn]

When I type echo $JAVA_HOME, Debian 11's Konsole displays ... nothing, 
'echo $PATH' reports - 
/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/snap/bin:libtool: 
/usr/bin/libtool /usr/share/libtool /usr/share/man/man1/libtool.1.gz -
However if I type, 'java --version' I get - 
/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/snap/bin:libtool: 
/usr/bin/libtool /usr/share/libtool /usr/share/man/man1/libtool.1.gz -, 
which is correct.
Where is $JAVA_HOME set or how do I add it to the path permanently?
Thanks in advance.