Well, first: is the class name "Room1" or "room1"?
Java cares -- it's case sensitive. Make sure you're typing the right one.
Have you compiled your class? In other words, is there now a file called Room1.class?
If all this is straightened out, then you may have a bad CLASSPATH setting. Try this:
java -cp . Room1
that's "java space dash cp space dot space Room1". That should work!