If you cannot pass a reasonable in-person interview, please do not respond,
e.g., if you do not know the difference between a programmer's newsgroup and a
jobs forum, or you're not willing to pay at least $200/hr (U.S.) plus expenses.

An abstract class is declared with the keyword "class" and is an
implementation, i.e., its methods can contain bodies.  It is also declared
"abstract", making it impossible to instantiate itself.  Its main purpose is
to root an inheritance tree with some behaviors predefined.  Inheritance from
an abstract class follows the single-inheritance rule - a child class may only
extend one parent class (or none, in the exceptional case of Object).  Some
methods of an abstract class may be declared "abstract", which means that the
method body is not provided in the abstract class but in its descendants for
polymorphic invocation.

An interface is a declaration (primarily) of public method signatures which
taken together represent a type with a defined contract for interaction with
other types.  (Interfaces may have no defined methods, in which case they
represent a type "marker".)  An interface's purpose is to define a type,
actually a supertype for classes to implement.  A class may implement any
number of interfaces, but for each interface it does implement, it must
provide method bodies for every method defined in the interface or be itself
an abstract class.

The primary differences are
- an interface defines a type whereas an abstract class defines a core
implementation,
- interfaces may be multiply implemented and may multiply inherit other
interfaces, but classes may only extend one parent class which itself might be
abstract,
- interfaces may not have instance variables, abstract classes may.

A "Type 1" JDBC driver is a bridge to an ODBC driver which in turn interacts
with the data store.  A "Type 4" JDBC driver is a driver written in Java
itself which directly uses the data store using the latter's native protocol.

My, my, how very generous.  If it's not open source, you do pay for it, right?

"If you can code"?  That's all you think a developer is?

Multiply by five and add expenses, bucko.