JAVA_HOME is the standard environment variable that indicates where a given version of Java is installed. The JAVA_HOME directory typically contains various directories (e.g., bin and lib). The environment variable may or may not actually be set for a given machine or user.

There are a variety of ways to search for JAVA_HOME.

On Debian 9, to see managed Java alternatives information, execute the commands below.

update-alternatives --list java

update-alternatives --display java

On Mac OS, JAVA_HOME is typically somewhere under directory /Library/Java/JavaVirtualMachines.

On Microsoft Windows, JAVA_HOME is typically somewhere under directory C:\Program Files\Java.