The Object Concept

An object is an encapsulation of data.

An object has

identity (a unique reference)

social security number (cpr), employee number, passport number

state, also called characteristics (variables)

hungry, sad, drunk, running, alive

behavior (methods)

eat, drink, wave, smile, kiss

An object is an instance of an class

A class is often called an Abstract Data Type (ADT).

Comments

Generalization and Specialization

Generalization creates a concept with a broader scope. Specialization creates a concept with a narrower scope. Reusing the interface! Inheritance: get the interface from the general class. Objects related by inheritance are all of the same type.

The Class Concept

A class is a collection of objects (or values) and a corresponding set of methods. A class encapsulates the data representation and makes data access possible at a higher level of abstraction. Example 1: A set of vehicles with operations for starting, stopping, driving, get km/liter, etc. Example 2: A time interval, start time, end time, duration, overlapping intervals, etc. Example 3: A string, upper case, compare, lower case, etc. str.equals(otherStr) – class/Java style strcmp(str, otherStr) – C style

JAVA

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