Saturday, 14 June 2014
“is a” and “has a” classes relationships
“is a” and “has
a” classes relationships
There are two ways we can do code reuse either by implementation of inheritance (IS-A relationship), or object composition (HAS-A relationship).
There are two ways we can do code reuse either by implementation of inheritance (IS-A relationship), or object composition (HAS-A relationship).
·
IS-A Relationship:- The concept of IS-A is a totally based on Inheritance, which
can be of two types Class Inheritance or Interface Inheritance. It is just like
saying "A is a B type of thing". For example, Apple is a Fruit, Car
is a Vehicle etc. Inheritance is uni-directional. For example House is a
Building. But Building is not a House.
It is key point to note that you can easily identify the IS-A relationship.
Wherever you see an extends keyword or implements keyword in a class
declaration, then this class is said to have IS-A relationship.
·
HAS-A
Relationship:- HAS-A simply
mean use of instance variables that are references to other objects. For
example: Suzuki has Engine, or House has Bathroom.
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