Interface's parent

Question

how can an interface has a parent? the parent i want is an abstract class. thanks

Answer 1

all those interfaces are actually DAOs. I want my DAOs to have the same parent. In the parent I want to define Connection as an instance variable with setter/getter. That connection will be passed from the DAO Factory. DAO methods will use that Connection to complete their work. This way I can make sure that in a use-case all DAOs use the same connection.
So instead of
public interface EmployeeDAO {
  public Employee getEmployeeById( int employeeId) throws EmployeeNotFoundException;
public class MSSqlServerEmployeeDAO implements EmployeeDAO {
  public Employee getEmployeeById( int employeeId) throws EmployeeNotFoundException {...}
}I would have
public abstract class ParentDAO {
private Connection connection = null;
public void setConnection(connection) {this.connection = connection;}
public Connection getConnection() {return this.connection;}
public abstract class EmployeeDAO extends ParentDAO {
  public abstract Employee getEmployeeById( int employeeId) throws EmployeeNotFoundException;
public class MSSqlServerEmployeeDAO extends EmployeeDAO {
  public Employee getEmployeeById( int employeeId) throws EmployeeNotFoundException {...}
}What do you think?