Lecture 2 classes i

Introduction to Computer Science II COSC 1320/6305 Lecture 2: Defining Classes I (Chapter 4)

Class Participation NetBeans Projects

Classes and Objects in Java Basics of Classes in Java

Contents ,[object Object],[object Object],[object Object]

Introduction ,[object Object],[object Object],[object Object],[object Object]

Classes ,[object Object],Circle centre radius circumference() area()

Classes ,[object Object],[object Object],[object Object],public class Circle { // my circle class } ,[object Object],[object Object],[object Object],[object Object],[object Object]

Adding Fields: Class Circle with fields ,[object Object],[object Object],public class Circle { public double x , y ; // center coordinate public double r ; // radius of the circle }

Adding Methods ,[object Object],[object Object],[object Object],type MethodName (parameter-list) { Method-body; }

Adding Methods to Class Circle public class Circle { public double x, y; // centre of the circle public double r; // radius of circle //Methods to return circumference and area public double circumference () { return 2*3.14*r; } public double area () { return 3.14 * r * r; } } Method Body public only for example purposes!!!!

Data Abstraction ,[object Object],[object Object],[object Object],[object Object]

Class of Circle ,[object Object],aCircle Points to nothing (Null Reference) bCircle Points to nothing (Null Reference) null null ,[object Object],[object Object]

Creating objects of a class ,[object Object],[object Object],bCircle = new Circle() ; aCircle = new Circle() ;

Creating objects of a class aCircle = new Circle() ; bCircle = new Circle() ; bCircle = aCircle ;

Creating objects of a class Q bCircle Before Assignment Q bCircle After Assignment aCircle = new Circle() ; bCircle = new Circle() ; bCircle = aCircle ; P aCircle P aCircle

Automatic garbage collection ,[object Object],[object Object],[object Object],Q

Accessing Object /Circle Data ,[object Object],Circle aCircle = new Circle() ; aCircle . x = 2.0; // initialize center and radius aCircle . y = 2.0; aCircle . r = 1.0; ObjectName . V ariableName ObjectName . MethodName (parameter-list)

Executing Methods in Object/Circle ,[object Object],Circle aCircle = new Circle() ; double area; aCircle . r = 1.0; area = aCircle . area (); sent ‘message’ to aCircle

Using Circle Class ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Radius=5.0 Area=78.5 Radius=5.0 Circumference =31.400000000000002

Summary ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Introduction ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],4-

A Class Is a Type ,[object Object],[object Object],[object Object],[object Object],4- CLASS Participation A!

A Sample Java Application Program 1-

System .out. println ,[object Object],[object Object],[object Object],[object Object],System .out. println ("This is an argument"); 1-

Variable declarations ,[object Object],[object Object],[object Object],1-

Using = and + ,[object Object],[object Object],[object Object],[object Object],[object Object],System.out.println("2 plus 2 is " + answer); 1-

Primitive Type Values vs. Class Type Values ,[object Object],[object Object],[object Object],[object Object],[object Object],4- CLASS Participation C! (pp. 188)

A Formal Parameter Used as a Local Variable ( BillingDialog.java ) 4-

The new Operator ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],4-

The Contents of a Class Definition ,[object Object],[object Object],[object Object],[object Object],4-

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Methods 4- Copyright © 2010 Pearson Addison-Wesley. All rights reserved.

main is a void Method ,[object Object],[object Object],[object Object],[object Object]

return Statements ,[object Object],[object Object],[object Object],[object Object],4-

Method Definitions ,[object Object],[object Object],[object Object],[object Object],[object Object],4-

Any Method Can Be Used As a void Method ,[object Object],[object Object],[object Object],4-

Local Variables ,[object Object],[object Object],[object Object],[object Object],4-

Parameters of a Primitive Type ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],4-

Parameters of a Primitive Type ,[object Object],[object Object],4-

Parameters of a Primitive Type ,[object Object],[object Object],[object Object],[object Object],4-

The this Parameter ,[object Object],[object Object],[object Object],[object Object],4-

Constructors ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],4- Copyright © 2010 Pearson Addison-Wesley. All rights reserved.

Lecture 2 classes i

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