COSC Week 3. J anuary 19, This week

Transcription

1 COSC Week 3. J anuary 19, This week Read chapters 2 & 16 of the text Attend your tutorial S how a partial solution to assignment #1 to your TA including some test cases Continue working on Assignment #1 1

2 Learning Objectives To learn about the software life cycle To learn how to discover new classes and methods To understand the use of CRC cards for class discovery To learn how to use object-oriented design to build complex programs Cost of Error Correction Cost of correcting errors grows with the size of the software Large projects cannot be done without advanced planning 1 in every 4 large software projects fails because of lack of planning 2

3 Cost of Correcting Errors As it happens :-) 3

4 Software Development S oftware development is Plan, Build, Deploy Plan is analyze, specify and design Build is code, debug and unit test Deploy is integration test, learn and maintain Software Development Process A formal process which identifies and describes various phases and provides guidelines for carrying out the phases The process consist of five phases Analysis Design Implementation Testing Deployment 4

5 Goals of Analysis To understand the problem To decide what the system is supposed to do To decide what the system is NOT supposed to do To prompt relevant questions about the system Goals of Design To develop a plan on how to implement the system To define the architecture of the system To decompose the software system into modules: classes to decide what each module should do, and to decide how modules should interact 5

6 Goals of Implementation To write and compile code to implement modules (classes) To finalize classes with all details added To verify that classes behave according to their specification (unit testing) Testing: Goals of Testing and Deployment To verify that the system behaves as required Deployment: To install it and use it for the intended purpose 6

7 Software Development Process S everal models have been used in practice Waterfall Model: formal process from 1970 s The S piral Model: Proposed by Boehm in 1988 Extreme Programming Proposed by Kent Beck on 1999 Waterfall Model (source: OOSC by Meyer) 7

8 Problems with Waterfall Approach is rigid cannot start the next phase before completing earlier phases Postpones detection and handling of risks to later phases. Risks include: Architectural- do subsystems work together? Requirements change- not what I wanted :-( Assumptions- client, analyst, designer, tester can make implicit incorrect assumption Iterative Models Iterative models reduce the risk by exposing them early on Waterfall model is followed within each iteration Each iteration adds more functionality to earlier products S piral Model and Extreme Programming are iterative approach 8

9 The Spiral Model Extreme Programming Development methodology that strives for simplicity by removing formal structure and focusing on best practices Realistic planning Customers make business decisions Programmers make technical decisions 9

10 Extreme Programming S mall releases Release a useful system quickly Release updates on a short cycle Pair programming Two programmers write code on the same computer Extreme Programming Continuous integration Build the entire system and test it whenever a task is complete Testing Programmers and customers write test cases Test continuously 10

11 Objec t-oriented Des ign Discover classes Determine responsibilities of each class Describe the relationships among the classes Discovering Classes A class represents some useful concept In most cases class represents an ADT Find classes by looking for nouns in the task description Define the behavior for each class Find methods by looking for verbs in the task description 11

12 CRC Card S tands for classes, responsibilities, collaborators Use an index card for each class Pick the class that should be responsible for each method (verb) Write the responsibility onto the class card Indicate what other classes are needed to fulfill the responsibility - the collaborators A CRC Card 12

13 Relations hips Between Classes Inheritance Association Dependency "Is-a" Relations hip The "is-a" relationship is inheritance; use extends o a circle is an ellipse o a car is a vehicle 13

14 "Has-a" Relations hip The "has-a" relationship is association; use an instance variable o a tire has a circle as its boundary o a car has a set of tires Us es Relations hip The "uses" relationship is dependency o an Applet uses a Graphics object 14

15 "is-a" and "has-a"example class Car extends Vehicle //inheritance "is-a" {... private Tire[] tires; //association "has-a" } Association and Dependenc y One class is associated with another if you can navigate from its objects to objects of the other class One class depends on another if it comes into contact with the other class in some way. Association is a stronger form of dependency 15

16 UML Notation for Inheritanc e and Association UML Relations hip Symbols 16

17 Five-Part Development Process Gather requirements Use CRC cards to find classes, responsibilities, and collaborators Use UML diagrams to record class relationships Use javadoc to document method behavior Implement your program Printing an Invoice - Requirements Print billing address, all line items, amount due Line item contains description, unit price, quantity ordered, total price 17

18 INVOICE Sample Invoic e S am's S mall Appliances 100 Main S treet Anytown, CA Description Price Qty Total Toaster Hair dryer Car vacuum Amount Due: $ Printing an Invoice - CRC Cards Discover classes Nouns are possible classes Invoice Price Address Item Product Description Quantity Total AmountDue 18

19 Printing an Invoice - CRC Cards Classes after a process of elimination Invoice Address Item Product CRC Cards for Printing Invoic e 19

20 CRC Cards for Printing Invoic e CRC Cards for Printing Invoic e 20

21 CRC Cards for Printing Invoic e Printing an Invoice - UML Diagrams The relationship between Invoice classes 21

22 Printing an Invoice - Method Doc umentation Use javadoc documentation comments to record the behavior of the classes Leave the body of the methods blank Run the javadoc utility to obtain a formatted version of the documentation in HTML format Method Doc umentation class /** Describes an invoice for a set of purchased products. */ class Invoice { /** Adds a charge for a product to this param aproduct the product that the customer param quantity the quantity of the product */ public void add(produc t aproduc t, int quantity) { } 22

23 /** Formats the invoic return the formatted invoic e */ public String format() { } } /** Computes the total amount Return the amount due */ public double getamountdue() { } Method Documentation - class /** Describes a quantity an article to purchase and its price. */ Class Item { /** Computes the total cost of this Return the total price */ public double gettotalpric e() { } 23

24 /** */ Formats this Return a formatted string of this item public String format() { } } Method Doc umentation - class /** Describes a product with a description and a price */ class Product { /** Gets the product Return the description */ public String getdes cription() { } /** Gets the product Return the unit price */ public double getpric e() { } } 24

25 Method Doc umentation - class /** Describes a mailing address. */ Class Address { /** Formats the Return the address as a string with 3 lines */ public S tring format() { } } The Class Documentation in the HTML Format 25

26 Printing an Invoice - Implementation The UML diagram will give instance variables o Look for associated classes o They yield instance variables Implementation Invoice is associated with Address and Item It will have Address and Item instance variables 26

27 Implementation An Invoice has one Address. o Declare one Address instance variable. Implementation An Invoice has multiple Items. o Use an ArrayList to hold Items. private ArrayList items 27

28 File Invoic etes t.java 01: import java.util.vector; 02: 03: /** 04: This program tests the invoice classes by printing 05: a sample invoice. 06: */ 07: public class InvoiceTest 08: { 09: public static void main(s tring[] args) 10: { 11: Address samsaddress 12: = new Address("S am's S mall Appliances", 13: "100 Main S treet", "Anytown", "CA", "98765"); 14: 15: Invoice samsinvoice = new Invoice(samsAddress); 16: samsinvoice.add(new Product("Toaster", 29.95), 3); 17: samsinvoice.add(new Product("Hair dryer", 24.95), 1); 18: samsinvoice.add(new Product("Car vacuum", 19.99), 2); 19: 20: S ystem.out.println(samsinvoice.format()); 21: } 22: } 28

29 File Invoic e.java 01: import java.util.arraylist; 02: 03: /** 04: Describes an invoice for a set of purchased products. 05: */ 06: class Invoice 07: { 08: /** 09: Constructs an invoice. param anaddress the billing address 11: */ 12: public Invoice(Address anaddress) 13: { 14: items = new ArrayList(); 15: billingaddress = anaddress; 16: } 17: 18: /** 19: Adds a charge for a product to this invoice. param aproduct the product that the customer ordered param quantity the quantity of the product 22: */ 23: public void add(product aproduct, int quantity) 24: { 25: Item anitem = new Item(aProduct, quantity); 26: items.add(anitem); 27: } 28: 29: /** 30: Formats the invoice. return the formatted invoice 32: */ 33: public S tring format() 34: { 35: S tring r = " I N V O I C E\n\n" 36: + billingaddress.format() 37: + "\n\ndescription Price Qty Total\n"; 29

30 38: for (int i = 0; i < items.size(); i++) 39: { 40: Item nextitem = (Item)items.get(i); 41: r = r + nextitem.format() + "\n"; 42: } 43: 44: r = r + "\namount DUE: $" + getamountdue(); 45: 46: return r; 47: } 48: 49: /** 50: Computes the total amount due. return the amount due 52: */ 53: public double getamountdue() 54: { 55: double amountdue = 0; 56: for (int i = 0; i < items.size(); i++) 57: { 58: Item nextitem = (Item)items.get(i); 59: amountdue = amountdue + nextitem.gettotalprice(); 60: } 61: return amountdue; 62: } 63: 64: private Address billingaddress; 65: private ArrayList items; 66: } 30

31 File Item.java 01: /** 02: Describes a quantity an article to purchase and its price. 03: */ 04: class Item 05: { 06: /** 07: Constructs an item from the product and quantity param aproduct the product param aquantity the item quantity 10: */ 11: public Item(Product aproduct, int aquantity) 12: { 13: theproduct = aproduct; 14: quantity = aquantity; 15: } 16: 17: /** 18: Computes the total cost of this item. return the total price 20: */ 21: public double gettotalprice() 22: { 23: return theproduct.getprice() * quantity; 24: } 25: 26: /** 27: Formats this item. return a formatted string of this item 29: */ 30: public S tring format() 31: { 32: final int COLUMN_WIDTH = 30; 33: S tring description = theproduct.getdescription(); 34: 35: S tring r = description; 36: 37: //pad with spaces to fill column 31

32 38: 39: int pad = COLUMN_WIDTH - description.length(); 40: for (int i = 1; i <= pad; i++) 41: r = r + " "; 42: 43: r = r + theproduct.getprice() 44: + " " + quantity 45: + " " + gettotalprice(); 46: 47: return r; 48: } 49: 50: private int quantity; 51: private Product theproduct; 52: } File Produc t.java 01: /** 02: Describes a product with a description and a price 03: */ 04: class Product 05: { 06: /** 07: Constructs a product from a description and a price. param adescription the product description param aprice the product price 10: */ 11: public Product(S tring adescription, double aprice) 12: { 13: description = adescription; 14: price = aprice; 15: } 16: 17: /** 32

33 18: Gets the product description. return the description 20: */ 21: public S tring getdescription() 22: { 23: return description; 24: } 25: 26: /** 27: Gets the product price. return the unit price 29: */ 30: public double getprice() 31: { 32: return price; 33: } 34: 35: private S tring description; 36: private double price; 37: } File Addres s.java 01: /** 02: Describes a mailing address. 03: */ 04: class Address 05: { 06: /** 07: Constructs a mailing address. param aname the recipient name param as treet the street param acity the city param as tate the 2-letter state code param azip the ZIP postal code 13: */ 14: public Address(S tring aname, S tring as treet, 15: S tring acity, S tring as tate, S tring azip) 16: { 17: name = aname; 18: street = as treet; 33

34 19: city = acity; 20: state = as tate; 21: zip = azip; 22: } 23: 24: /** 25: Formats the address. return the address as a string with 3 lines 27: */ 28: public S tring format() 29: { 30: return name + "\n" + street + "\n" 31: + city + ", " + state + " " + zip; 32: } 33: 34: private S tring name; 35: private S tring street; 36: private S tring city; 37: private S tring state; 38: private S tring zip; 39: } Summary S lides are on the web Work on assignment 1 S how partial solution to TA this week Assignment due next week Do the reading Chapter 2 & 16 of the text 34