# Class 21 - Methods, continued 1 Goals for Today n n Build a...

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Methods, continued 1

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Goals for Today n Build a method library n Distinguish between class and instance methods 2 MGMT 29000
Method Libraries n Repositories for related methods n Example: Math class n Section objective: build two method libraries 3 MGMT 29000

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Problem Description: Ballooning a Bedroom n Problem context ¨ Your friend who plays practical jokes is away ¨ You want to play a practical joke on your friend ¨ You plan to fill your friend’s room with balloons n Question: how many balloons should you purchase n The question will be answered by a program 4 MGMT 29000
Program Design n The problem is concerned with volumes ¨ Find out how many balloon volumes fit in a room volume n The balloon is approximated by a sphere ¨ volumesphere = 4/3 x PI x radius3 n The room is approximated by a box ¨ volumebox = length x width x height n Another issue: whether to use large or small balloons ¨ Large balloons take long to inflate, but fewer are needed ¨ Small balloons inflate quickly, but more are needed 5 MGMT 29000

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Program Design (continued) n Essentials of the user story ¨ Query the user for the radius of the balloon ¨ Read the radius from the keyboard ¨ Compute the volume of one balloon ¨ Compute the volume of the bedroom n Note: dimensions of room are declared as constants ¨ Compute number of balloons needed to fill the bedroom ¨ Display the required number of balloons, with labels n Identify nouns and verbs to find objects and operations n Organize objects and operations into an algorithm MGMT 29000 6
Program Design (continued) MGMT 29000 7

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Program Design (continued) MGMT 29000 8
Program Design (continued) MGMT 29000 9

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Program Implementation n First decision: write methods to compute volumes ¨ Rationale: methods allow computations to be reused n Second decision: store methods in separate classes ¨ Rationale: makes the program more modular n Three classes will be used to implement the program ¨ BalloonPrank : contains the main() driver method ¨ Sphere : library containing sphere methods ¨ Box : library containing box methods n Sphere.volume() : takes one argument (radius) n Box.volume() : takes three arguments (l, w, h) MGMT 29000 10
Program Implementation (continued) MGMT 29000 11

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Program Implementation (continued) MGMT 29000 12
Program Implementation (continued) MGMT 29000 13

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Unit Testing n The sole purpose of a test class ¨ Ensure that methods in the program or library work n
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## This note was uploaded on 04/04/2012 for the course MGMT 290 taught by Professor Staff during the Fall '08 term at Purdue University-West Lafayette.

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Class 21 - Methods, continued 1 Goals for Today n n Build a...

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