interface Java Keyword

The interface keyword is used to declare a new Java interface, which is a collection of methods.
Interfaces are a powerful feature of the Java language. Any class may declare that it implements one or more
interfaces, meaining it implements all of the methods defined in those interfaces.

Examples

public interface IPolygon
{
public float getArea();
public int getNumberOfSides();
public int getCircumference();
}

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

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).

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