I have two suggestions to help you fix this:
1) Make sure you have "package estructuras;" at the top of the PuntoI.java file.
2) Delete all .class files before you compile again.
If you are interested in revisiting setting the PATH so you can compile from the command line, you should check out step 5 in the
Java Installation Notes. I think this might be your best bet. Otherwise, you will have to figure out how to set the classpath under JGrasp. I'll be willing to help you either way, but I'm already familiar with the command-line. It will take more time to figure out how to do all this in JGrasp instead.
Also, are you placing the Punto2Di class in the estructuras package (i.e. does Punto2Di.java have "package estructuras;" at the top)? From the output in your most recent post, you obviously moved the file, but did you change the source code so that Java knows it's in a different package? Also, Note that you do not need to import classes that are in the same package. So when you try with Punto2Di in the estructuras package, you don't need the "import estructuras.*;" statement at all. Perhaps removing this line will fix the errors. At least it will give different errors for us to work with.
Well, let me know if any of these suggestions help you.
Regards,
Layne