Object-Oriented Designs

Chapter 6
Object-Oriented Designs

Programs are written to perform tasks.
Object-oriented programming employs computational objects to perform the tasks.
Different objects are allocated different assignments, and the objects cooperate to solve the problem
The benefit: a mechanism for reducing complexity.

Objects have reference values, called also handles, through which they can be accessed.
The handles may be used for expressing relationships between objects
The handles may be used for addressing messages to objects

Issues to be considered

Issues to be considered

Different objects having the same functionalities and properties are members of the same class.
The members of a class are said to be instances of the class
Features of the instances of a class are called instance features
Features shared by the instances of a class are said to be class features
Subclasses of a class inherit the features of the class

Class name:	Apple

Instance properties (instance fields):	color, weight
Class properties (class fields):	count, weight
Constructor:	adds an apple of specified color and weight, and adjusts the class fields
Methods:

Instance locators (instance handlers):	apple 1, apple 2
Instance states:	state(apple 1)=(green, 0.25 pound), state(apple 2)=(red, 0.3 pound)
Class state:	(2, 0.55 pound)

Class name:	Clock

Instance properties (instance fields):	hours, minutes, seconds
Class properties (class fields):	max time min time total cost
Constructor:	adds a clock set to the requested time
Instance functions (methods):	advance the time by one second set the clock to a requested time display the clock time
Class functions (methods):	show average (of min and max) time

Instance locators (instance handlers):	early, late
Instance states:	state(early) = 3:00:00, state(late) = 5:45:22
Class state:	state = (3:00:00, 5:45:22)

Notes

Methods are typically of little interest if they don’t refer to fields.
Class methods may, and normally do, directly refer to class fields. They can’t directly refer to instance fields.
Instance methods and constructors may directly refer to instance and class methods

Due: Mo, Apr 21, midnight

Write a report which offers a class of objects of your liking and shows the following features.

Note: none of the above items should be empty.

Assume ‘lab7’ for the submit program.