Apex and salesforce

I am new to salesforce and apex as well. trying to use to understand both while working. I was wondering about following things

1. Is it possiable to run the Java code inside Salesforce, instead of Apex?

2. Is it possible to have packages in the Apex code so that I could enable the like wide classed together?

3. Is there any easy way to debug an Apex application on my local system? At present I am trying to put system.debug and execute it with Salesforce.

4. Can I configure the environment variable in the salesforce and use it in the Apex?

Thanks a lot for helping me out

• You cannot run Java. Only Apex.
• Not sure what you mean by packages. Apex doesn't have anything like Java packages.
• There is no local debugging or local engine. Only runs in the cloud.
• For environment variables, custom settings are probably the closest analog.