mkgmap & Unsupported major.minor version 51.0

After editing late in the day, I am trying to make a new map to load on my eTrex that highlights the remaining un-named ways for the next day, using mkgmap and a download of an .osm file using Josm of part of a suburb, using the following command as an initial trial.

java -jar /Applications/mkgmap-r3118/mkgmap.jar --gmapsupp --style=noname /Users/xxxx/Documents/JOSM/Save_OSM_file/nonametest.osm

and I get the following advice…

I assume a version incompatibility with mkgmap and my java version

java -version
java version “1.6.0_65”
Java™ SE Runtime Environment (build 1.6.0_65-b14-462-10M4609)
Java HotSpot™ 64-Bit Server VM (build 20.65-b04-462, mixed mode)

I can’t run java 1.7 on this machine (would it help if I used a later mac that could?)

System Version: Mac OS X 10.6.8 (10K549) Snow Leopard
Kernel Version: Darwin 10.8.0

I also tried these commands with the same result…
java -jar /Applications/mkgmap-r3118/mkgmap.jar --list-styles
java -jar /Applications/mkgmap-r3118/mkgmap.jar --version

I would appreciate a point in the next direction please…

Does the info below confirm that I must run java 7 for mkgmap?

Further Edit:

…belatedly found this

That seems plain enough even for me now - I must have a later Java version installed and this can’t be done on this machine?
Is it likely that the developers of mkgmap will recompile a version of the program in the near future so that it runs under java 1.6?

As far as I know Java 1.6 isnt supported anymore, better ask it on the mkgmap development list: