I am not sure I quite understood your question...
1. If you have more than 1 top level classes, only 1 can be public. The other can be private, protected or default access.
When you say what is the default....well, when you have no access modifier, its the package access or default access and thats the default
2. For inner classes, you can have any access modifier - Public, Private, protected or default. Again if you don't give it any access modifier - it is the default access.
Monisha.