Programming Techniques Laboratory 1 OOP Principles

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Emerald Reed
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1 Programming Techniques Laboratory 1 OOP Principles Finance Application

Identification code The results will offer information about the

2 Purpose Develop an application that allows you to query different types of company considering the following filters: Name City Identification code The results will offer information about the number of employees and the profit of the firm during the last year.

3 Development(1) 1. Approach (C)... int n = 10; string name[n], id[n], city[n]; int profit[n], noemployees[n]; 1. Write the data structures representing companies ( name, city, id, profit, number of employees) Represent data as arrays. The information corresponding to the firm will be represented at the same index in the arrays

4 Development(2) 2. Sort the companies by profit Sort the profit array. When swapping the profit values, the corresponding values from all the other arrays need to be swapped as well 1. Approach (C)... for(int i=0;i<n;i++) for(int j=0;j<n;j++) if(profit[i]>profit[j]) swap(profit[i], profit[j]); swap(name[i], name[j]);...

5 Development(3) 2. Sort the companies by profit Sort the profit array. When swapping the profit values, the corresponding values from all the other arrays need to be swapped as well => error prone & inefficient => Solution : array of structs 1. Approach (C) typedef struct Company string name; string id; string city; int noemployees; ; Company list[n]; for(int i=0;i<n;i++) for(int j=0;j<n;j++) if(list[i].profit>lista[j].profit) swap(list[i],list[j]);

6 Development(4) 3. Represent another type of firm called "Sole Trader" and include information about the birth year of the owner. The sole trader is a firm that has only one employee, which is the actual owner; 1. Approach (C) typedef struct SoleTrader string name; string id; string city; Int birthyear; ; SoleTrader list[n]; for(int i=0;i<n;i++) for(int j=0;j<n;j++) if(list[i].profit>lista[j].profit) swap(list[i],list[j]);

7 Development(5) 4. Add functionality to the program, in order to a) compute the VAT for each type of company b) print the details of each company. Problem 1: code duplication! Problem 2: how can the functionality corresponding to the same data structure be grouped? 1. Approach (C) void computecompanytax( Company c) double percentage = 0.2; cout<<percentage*c.profit; void computesoletradertax( SoleTrader s) double percentage = 0.2; cout<<percentage*s.profit; void printcompany( Company c) cout<<c.name + " " + c.noemployees; void printsoletrader( SoleTrader s) cout<<s.name + " " + s.birthyear;

8 Development(6) 4. Add functionality to the program, in order to a) compute the VAT for each type of company b) print the details of each company. Problem 1: code duplication! Problem 2: how can the functionality corresponding to the same data structure be grouped? 1. Approach (C) typedef struct Company string name; string id; string city; int noemployees; ; typedef struct SoleTrader string name; string id; string city; Int birthyear; ;

9 Development(7) 4. Add functionality to the program, in order to a) compute the VAT for each type of company b) print the details of each company. Problem 1: code duplication! Problem 2: how can the functionality corresponding to the same data structure be grouped? 1. Approach (C) typedef struct Company string name; string id; string city; int noemployees; ; typedef struct SoleTrader string name; string id; string city; Int birthyear; ; Solution: Develop app using classes

10 Development(8) 1. Write the data structures representing companies ( name, city, id, profit, number of employees) Represent data as a class 2. Approach (Java) public class Company String name; String id; String city; int noemployees; ABSTRACTION

11 Development(9) 3. Represent another type of company called "Sole Trader" and include information about the birth year of the owner. 2. Approach (Java) public class SoleTrader String name; String id; String city; int birthyear;

12 Development(10) 4. Add functionality to the program, in order to a) compute the VAT for each type of company b) print the details of each company. 2. Approach (Java) public class SoleTrader String name; String id; String city; int birthyear; void computetax() double percentage = 0.2; System.out.println(percentage*profit); void print() System.out.println(name + " " + birthyear);

13 Development(11) 4. Add functionality to the program, in order to a) compute the VAT for each type of company b) print the details of each company. How do we remove the duplicate code? 2. Approach (Java) public class Company String name; String id; String city; int birthyear; void computetax() double percentage = 0.2; System.out.println(percentage*profit); void print() System.out.println(name + " " + birthyear);

14 Development(12) How do we remove the duplicate code? Solution: INHERITANCE 2. Approach (Java) public class GeneralFirm String name; String id; String city; void computetax( ) double percentage = 0.2; System.out.println(percentage*profit); void print() System.out.println(name); public class SoleTrader extends GeneralFirm int birthyear; void print() System.out.println(name + " " + birthyear); public class Company extends GeneralFirm int noemployees; void print() System.out.println(name + " " + noemployees);

15 Development(13) POLYMORPHISM What happens with the print method? Which one will be called? public class SoleTrader extends GeneralFirm int birthyear; void print() System.out.println(name + " " + birthyear); public class Company extends GeneralFirm int noemployees; void print() System.out.println(name + " " + noemployees);

16 Development(14) POLYMORPHISM GeneralFirm firm1 = new GeneralFirm( ); GeneralFirm firm2 = new SoleTrader( ); GeneralFirm firm3 = new Company( ); firm1.print(); firm2.print(); firm3.print(); >> Same type, multiple forms = polymorphism public class SoleTrader extends GeneralFirm int birthyear; void print() System.out.println(name + " " + birthyear); public class Company extends GeneralFirm int noemployees; void print() System.out.println(name + " " + noemployees);

Development(15) ENCAPSULATION ensure the integrity of the data and restrict the direct access to the class's fields ex. Consider the noemployees field.

17 Development(15) ENCAPSULATION ensure the integrity of the data and restrict the direct access to the class's fields ex. Consider the noemployees field. Encapsulation will ensure that the property will have a consistent state by: - not allowing direct access to the field; - establishing business rules to ensure the integrity public void setnoemployees( int noemployee) If(noEmployee <0)return; this.noemployee = noemployee; 2. Approach (Java) public class GeneralFirm private String name; private String id; private String city; private public void computetax( ) double percentage = 0.2; System.out.println(percentage*profit); public void print() System.out.println(name); public void setname(string name) This.name = name; public void getname() return name; //... getters and setters for all fields

Notes on Chapter Three

Notes on Chapter Three Methods 1. A Method is a named block of code that can be executed by using the method name. When the code in the method has completed it will return to the place it was called in