Is it possible to run Sun's JDK 6 alongside a later version of openJDK?

I have openJDK 1.8 installed but I also need Sun’s JDK 6 for a project (I also need Java 8 for my IDE). Do I need to uninstall openJDK or can they exist side by side?

they can live side by side but oracle’s rpm is buggy it needs some massaging to make it work with update-alternatives see this thread
and edit that script to make it work with java 6
that thread is about the java runtime you might need to tweak the java compiler javac too
also check

man update-alternatives

Are you sure I need that? JDK 6 isn’t being updated anymore, so after I install it, that should be the last time it changes.

I downloaded a “.bin” and it simply extracted the files into a directory.

the thing with java (any version) is that opensuse can have multiple versions and you need to use update-alternatives to set the currently used java runtime and compiler, maybe the run file is better then the rpm so try running

update-alternatives --config java
update-alternatives --config javac

and see what happens
check this rhle doc about using update-alternatives and java (it’s about jdk6)

and one from sle