How do you express an ‘is a’ relationship and a ‘has a’ relationship or explain inheritance and composition? What is the difference between compositio

The ‘is a’ relationship is expressed with inheritance and ‘has a’ relationship is expressed with composition. Both inheritance and composition allow you to place sub-objects inside your new class. Two of the main techniques for code reuse are class inheritance and object composition.

Inheritance [ is a ] Vs Composition [ has a ] Building Bathroom House

class Building{

.......

}

class House extends Building{

.........

}

is a [House is a Building]

class House {

Bathroom room = new Bathroom() ;

....

public void getTotMirrors(){

room.getNoMirrors();

....

}

}

is a has a [House has a Bathroom] has a Inheritance is uni-directional. For example House is a Building. But Building is not a House. Inheritance uses extends key word. Composition: is used when House has a Bathroom. It is incorrect to say House is a Bathroom. Composition simply means using instance variables that refer to other objects. The class House will have an instance variable, which refers to a Bathroom object.