Yes it is probably not possible to run .jar files in classic mac. I installed Netscape 3.0 and it run local html files with java but not .jar files. The same with IE 4.01 full version. There is OpenDoc stationery that i suppose should run java applets but it says "applet loading..." and nothing...
Is it possible to run .jar java programs in LC 630? It has the System 7.5.5. OS installed. Or are there any double-window filemanagers for 68k Macs? (Norton commander look-a-like).