1. Check the default Java version

java -version

Output example:

(base) ~ % java -version                                  
openjdk version "21.0.9" 2025-10-21
OpenJDK Runtime Environment Homebrew (build 21.0.9)
OpenJDK 64-Bit Server VM Homebrew (build 21.0.9, mixed mode, sharing)

2. Check the Java compiler version

javac -version

3. Check installed Java versions on Mac

/usr/libexec/java_home -V

4. Check JAVA_HOME

echo $JAVA_HOME