Bash command to check if Oracle or OpenJDK java version is installed on Linux

if [[ $(java -version 2>&1) == *"OpenJDK"* ]]; then echo ok; else echo 'not ok'; fi

java -version 2>&1 | grep "OpenJDK Runtime" | wc -l

returns 0 if using Oracle JDK, 1 if using OpenJDK

Bash condition:

if [[ $(java -version 2>&1 | grep "OpenJDK Runtime") ]]