INSTANCE
• Instance is an Object of a class which is an entity with its own attribute values and methods.
Creating an Instance :
ClassName refVariable;
refVariable = new Constructor();
or
ClassName refVariable = new Constructor();
Java Class Hierarchy
• In Java, class “Object” is the base class to all other classes
– If we do not explicitly say extends in a new class definition,
it implicitly extends Object
– The tree of classes that extend from Object and all of its
subclasses are is called the class hierarchy
– All classes eventually lead back up to Object
– This will enable consistent access of objects of different
classes.
Inheritance
• Methods allows to reuse a sequence of statements
• Inheritance allows to reuse classes by deriving a new class
from an existing one
• The existing class is called the parent class, or superclass, or
base class
• The derived class is called the child class or subclass.
• The child class inherits characteristics of the parent class(i.e
the child class inherits the methods and data defined for the
parent class
• Inheritance relationships are often shown graphically
in a class diagram, with the arrow pointing to the
parent class