cshao

If you just start learning Java, recommend that you use command prompt.

"Java in a Nutshell" is a good book for programmer, however, I don't think it's a good book for beginner without any programming experience.You can try "Head First Java", that's better if you don't have any coding experience.

null does not have any method, including equals(), so if id is null, id.equals(...) will generate NullPointerException.