How to design a DAO class? [closed]

Answer 1

To have more abstraction :

interface IDAO {

  public save(T t);
  public T getById(int id);
  //...etc

}

then

public CustomerDao implements IDAO{
   public save(Customer c){
        //Code here
    }
   public Customer getById(int id){
      //Code here
    }
}

and DAO tO another domain

public UniversityDao implements IDAO{

     public save(University u){
       //Code here
      }
     public University getById(int id){
        //Code here
     }
}

Now the presentation layer or the main Class will contain the code like this :

IDAO  dao;
dao=new CustomerDao();
//...
dao=new UniversityDao();