javac : command not found
You installed the Java Runtime Environment (JRE) only, which does not provide javac. For javac, you have to install the OpenJDK Development Environment. You can install java-devel or java-11-devel, which both include javac.
By the way: you can find out which package provides javac with a yum search, e.g.
su -c 'yum provides javac'on more recent releases of CentOS e.g. 6 the command changes to
su -c 'yum provides */javac'
Use the following sudo command:
sudo yum install java-1.6.0-openjdk-devel