1. Object-oriented Design in Processing
B. Ramamurthy
Pages

2. The OO Concept
When you write small programs functional decomposition or collection of function efficiently solve the problem
When you solve complex problem with multiple objects interacting, a better and proven way to design the solution is using Object-oriented design (OOD).
When you implement a OOD using an object-oriented programming language it is called a object-oriented program.
We will study here the foundations of OOD and OOP.

3. Object-Oriented Principles
OOP
Inheritance
-- Hierarchy
-- Reusability
-- Extensibility
-- Expressive power
-- Reflects many
real-world problems
Polymorphism
-- Many forms of
same function
Encapsulation
(class)
-- Information Hiding
-- Interface and
Implementations
-- Standardization
-- Access Control mechanisms
(private /public etc.)
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4. What is an Object?
Object-oriented programming supports the view that programs are composed of objects that interact with one another.
How would you describe an object?
Using its characteristics (has a ----?) and its behaviors (can do ----?)
Object must have unique identity (name) : Basketball, Blue ball
Consider a ball:
Color and diameter are characteristics (Data Declarations)
throw, bounce, roll are behaviors (Methods)
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5. Classes are Blueprints
A class defines the general nature of a collection of objects of the same type.
The process creating an object from a class is called instantiation.
Every object is an instance of a particular class.
There can be many instances of objects from the same class possible with different values for data.
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6. Example objects Object References redRose class Rose blueRose class
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7. Bouquet Class Many instances of real bouquet objects of this Class
can be instantiated
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8. Elements of a Class class data declarations (variables, constants)
methods
header
body
header
statements
modifiers,
type, name
variables,
constants
parameters
repetition
others
selection
assignment
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9. Class Structure
class
variables
constants
methods
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10. Defining Classes Syntax: class class_name { data-declarations
constructors
methods }
Constructors are special methods used for instantiating (or creating) objects from a class.
Data declarations are implemented using variable and constant declarations.
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11. Operator new and “dot”
new operator creates a object and returns a reference to that object.
After an object has been instantiated, you can use dot operator to access its methods and data declarations (if you have access permissions).
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12. Example
Ball Class
Class is an object blueprint; you can create as many objects as you need from a class
Objects have attributes/characteristics
Objects have behavior/capabilities/operations/functions
Need a function to create an object… called a constructor
There can more than one constructor for a class depending on the parameters

13. Class Ball
class ball { // attributes float x, y; //position color ballColor; float radius; // operations //constructor ball() { x = random(width); y = random(height); ballColor = color(255, 0, 0); radius = 25; }

14. Add display behavior
void display() { noStroke(); fill(ballColor); ellipse(x,y,2*radius, 2*radius); } Lets see how this works. How to create a ball? Using its constructor: Example b1 = new ball();

15. Box Class
Lets add a box class
And create many balls in the box class.