- A class,
is like a definition
of a data type in
Java
- An instance of an
object of a given
class is
created (= instantiated)
using
a constructor and the
new operator.
- Object instances in
Java
are accessed through
reference variables.
- A subclass
can extend a
superclass and
use its
methods and
instance
variables
through inheritance and
polymorphism.
- Abstract classes
can contain 0 or more
abstract methods
Classes
containing at least one
abstract method
must be abstract
Abstract classes
can not be used
to instantiate objects
Abstract classes are
extended by a
subclass that
defines the
abstract methods.
- Interfaces
contain only
abstract methods and
constants and
provides a
template for another
class
to implement
all of the methods
declared in the interface.
|