You could remove OpenJDK JRE without any problem or leave it just the same.
Java is a technology from Oracle (formerly: Sun Microsystems). There are several implementations:
OpenJDK: The primary goal of the OpenJDK project is to produce an
open-source implementation of the Java SE Platform (6 and 7). This
is the default version of Java that Ubuntu uses and is the easiest
Oracle (Sun) Java 6: Oracle (Sun) Java 6 is the reference implementation for Java 6.
Oracle Java 7: Oracle Java 7 is the reference implementation for Java 7.
IBM Java: IBM Java is the preferred Java solution on PowerPC machines. It is a reimplementation with a Just-In-Time Compiler. It is only available from IBM's website.
To manage your Java version/flavour in terminal use
update-alternatives, to list the available java versions
update-alternatives --list java.
If you'd wish all could be installed without issues, and you could choose witch one to use using
update-alternatives --config java**
Please take note that java as four components, they must all be configured to you preference.
java Java Runtime Environment (JRE);
javaws Java Web Start, Java application over the net;
javac Java Compiler, JDK for Developers;
- And of course the browser plugin, currently mine is
firefox is easy to find out yours just type
about:plugins in the address bar.
Normally the several java flavors/versions are in
/usr/lib/jvm, me, for example have OpenJDK and two different versions of Oracle-Java.