Lec 13 Writing an Instantiable Class II

Agenda

• Adding to our Balloon Class demo:– default Constructor method– inflate method that takes a parameter (amount)– pop method– volume method

Recall Structure of an Instantiable Class

class Balloon

sizecolor

BallooninflategetSizegetColorsetColorpop

Class NameInstance Varbls

Methods

Constructor methodsame name as class

Method Overloading• We can add methods to Balloon with same names

– as long as have different parameters– the Constructor we made in our Balloon class

– A second "Default" constructor with no parameters

Which one is used?

• Balloon myBal = new Balloon(10,Color.RED);

• Balloon yrBal = new Balloon();

• default constructor automatically – sets size to 0– sets color to Color.WHITE

Now we'll begin BalloonDemo2

• start with BalloonDemo from last time• add default constructor• add inflate method that takes an amount• add pop method

– modify both inflate methods• add volume method

– should return 0 if balloon has been popped

More Dairy.java

• make Lab13DairyFarm folder• Copy, Dairy.java file from Lab12 folder, then add

– default Constructor– addCow takes a number– calcMllkProfit takes a price/gallon– calcButterProfit takes a price/pound

• Create a new class Farm.java that– tests your new Dairy class by constructing a dairy farm,

adding cows and printing the number of cows– And printing profit from selling milk or butter