Re: Noob + Java = Questions;
1) Suppose you and I both create a class Foo, each in its own package, say mypackage.Foo and yourpackage.Foo; which class is the compiler to use when it has to compile a class that uses a class Foo?
2) Efficiency, both space and speedwise;
3) I think you mean paotability here, not probability; Java can be quite fast, thanks to its JIT compilation (to raw macine code) and it can be made secure by use of a SecurityManager that forbids a program to execute potentially unsafe operations and Java is portable in a way that you only have to "compiler once and run anywhere".
4) This also is a wide concept and I don't know what you really mean by this.
5) A project (a bunch of classes) can have several classes with a 'main' class or none. What is Eclipse (or any other ide) supposed to create?