At the moment, the answer is no. There is a way but it is not so easy: OpenJDK with MicroEmulator + a skin to ease use, then you have to download and start .jad or .jar files in MicroEmu.
Working, slowly because Java bytecode is interpreted and JVM+MicroEmu requires too much memory.
That is why I'm working on the port of Symbian JRT http://developer.symbian.org/wiki/JRT as a proof of concept. For a real end-user deployment, I guess we will face many licensing and royalties issues...
Since it's just a tarball which can be unpacked to a directory of your choice, it should be possible to use it without uninstalling OpenJDK first (I didn't test it). Of course, as long as the OpenJDK "java" binary is linked to /usr/bin/java, you will always have to specify the full path to the Sun "java" binary in order to use it.
I have compared MicroEmulator startup with OpenJDK and Oracle JavaSE embedded (armv7, headful) and Oracle JavaSE runs a little faster.
If you want it to be used for MicroEmulator, edit /usr/bin/microemulator script and replace "java" by the full path to the location where you extract Oracle JavaSE embedded.
