check java cmd
root@debko:~# which java
/usr/bin/java
check java path
root@debko:~# ls -la /usr/bin/java
lrwxrwxrwx 1 root root 22 Aug 31 17:18 /usr/bin/java -> /etc/alternatives/java
root@debko:~# ls -al /etc/alternatives/java
lrwxrwxrwx 1 root root 46 Aug 31 17:18 /etc/alternatives/java -> /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java
set java path
root@debko:~# tail -n2 /etc/profile
export JAVA_HOME=$(dirname $(dirname $(readlink -f /usr/bin/java)))
export PATH=$PATH:$JAVA_HOME/bin/