There are different verticals in which Java Classes can be classified.
1. Access - Public , Private , default or Protected.
2. Packaging - System, library or User Defined
3. Structure - Outer or Inner
4. Object Derivation - Abstract Class or Concrete Class.
5. Object Creation - Normal, Singleton , Doubleton , Immutable or Enum.
6. Functionality - String , Util , Stream etc.
1. Access - Public , Private , default or Protected.
2. Packaging - System, library or User Defined
3. Structure - Outer or Inner
4. Object Derivation - Abstract Class or Concrete Class.
5. Object Creation - Normal, Singleton , Doubleton , Immutable or Enum.
6. Functionality - String , Util , Stream etc.