You can only use protected classes within the same package, or through inheritance (i.e. another class subclassing the protected class). Read up a little bit on
java class modifiers to get a good briefing on this subject, the 3 access modifiers are public, protected, and private. But there are four access levels, public, protected, default, and private. Default is only used when you do not specify another modifier, and it means package level access (i.e. only classes in the same package can access that class).