sep 2005 sdp-msc slide 1 section 7 object oriented programming

Sep 2005 SDP-MSc Slide

1

Section 7

Object Oriented Programming


2


Section 7.1

Class Definition

using System;

class Counter{ private int number; private string name; public Counter(int v, String n){ this.number = v;

this.name = n;}

public void increment(){this.number++;}

public int read_value(){ return this.number;}

}

public class Ex1{

public static void Main(){

Counter c1; c1=new Counter(6, "Days");

c1.increment(); c1.increment(); int res=c1.read_value(); Console.WriteLine("Value: {0}",res); }

}

public class Ex1{public static void Main(){ Counter c1=new Counter(6,"Days Worked");

int choice=0; while (choice !=3){

Console.WriteLine(":");Console.WriteLine("1: Increment");Console.WriteLine("2: Read Value");Console.WriteLine("3: Exit");Console.Write("Enter Choice: ");string temp=Console.ReadLine();

choice=Convert.ToInt32(temp);switch(choice){ case 1: c1.increment(); break; case 2: int res=c1.read_value(); Console.WriteLine(": {0}",res); break; }}}}

Alternative Test Fn


6

Allows Read/Write access to member data:

class Counter{ private string name; private int number; public int NUMBER{ get { return number;} set { number=value;} // ‘value’ a keyword } public Counter(int v, String n){ this.number = v;

this.name = n;}

public void increment(){this.number++;}

public int read_value(){ return this.number;}

}

Properties

public class Ex1{


Counter c1; c1=new Counter(6, "Days");

c1.NUMBER=9; c1.increment(); c1.increment(); int res=c1.NUMBER; Console.WriteLine("Value: {0}",res); }

}

Properties

class Account{ private int accNo; private int balance; public Account(int No, int bal){ this.balance=bal;

this.accNo=No;}public int getAccNo(){return accNo;}

public int getBalance() {return balance;}

public void credit(int amount){ balance+=amount;}

public void print_details(){ System.out.print("\nAccount Details”+ “\nNo:”); System.out.println(accNo+" Balance:"+balance);}}


10

public class Ex2{


Account a1 = new Account(1,100); Account a2 = new Account(2,200); a1.credit(50); a1.print_details(); a2.print_details(); }}


11

Account DetailsNo:1 Balance:150



12

public class Ex1{public static void Main(){ Account a1 = new Account(1,100);

int amt=0, choice=0; while (choice !=3){

Console.WriteLine(":");Console.WriteLine("1: Deposit");Console.WriteLine("2: Check Balance");Console.WriteLine("3: Exit");Console.Write("Enter Choice:");

choice=Convert.ToInt32(Console.ReadLine());switch(choice){

case 1: Console.WriteLine("Enter Amount"); amt=Convert.ToInt32(Console.ReadLine());

a1.credit(amt); break;case 2: a1.print_details(); break;

} }}}

Alternative Test Fn


13

Alternative Version using properties

get, set


14


this.accNo=No;}public int Account_No{

get {return accNo;} set {accNo= value;}}

public int getBalance { get{return balance;}} // only read access


public void print_details(){ Console.Write("Details"+ ":"); Console.WriteLine("{0} Balance: {1}",accNo,balance);}}:


15

public class Ex1{


Account a1 = new Account(1,100); Account a2 = new Account(2,200);

a1.Account_No=678; // set int res=a1.getBalance; // get

Console.WriteLine("a1 bal={0}",res); a1.print_details(); a2.print_details(); }

}


16

Indexers

Array type indexing of a class object


17

class Vector{ private int count=4;private int []arr={3,3,6,7};

public int this[int index]{get{ if (index < count) return arr[index]; else return 0;}

set { arr[index]=value;}}} }

:


18

public class Ex1{


Vector v =new Vector(); v[1]=9; // setConsole.WriteLine("value={0}",v[1]); // get

}}


19

class LList{private int[] list;private int count;private int size;

public LList(int s){ this.size=s; this.count=0;

this.list=new int[s];}

public void insert(int v){ if (count<size){

list[count]=v; count++;}}:


20

:

public void print_LList(){ Console.WriteLine("");

for(int i=0;i<count;i++){ Console.WriteLine(" {0}",list[i]);

}}

}


21

public class Ex1{

public static void Main(){ LList s = new LList(5);

int val=0, choice=0;while (choice !=3){

Console.WriteLine(":");Console.WriteLine("1: Insert");Console.WriteLine("2: Print Stack");Console.WriteLine("3: Exit"); :


22

:Console.Write("Enter Choice:");

choice=Convert.ToInt32(Console.ReadLine());

switch(choice){ case 1: Console.Write("Enter Value");

val=Convert.ToInt32(Console.ReadLine()); s.insert(val); break;

case 2: s.print_LList(); break; } } }}


23

• Version 2 of Account Class

- static variables


24

class Account{ private int accNo; private int balance; private static int count=0; public Account(int bal){ this.balance=bal;

this.accNo=++count;}

public int getAccNo(){return accNo;}


public static int read_count(){return count;}

public void credit(int amount){ balance+=amount;}:

}


25

public class Ex1{

public static void Main(){ Account a1 = new Account(100);

Account a2 = new Account(200); a1.credit(50); a1.print_details(); a2.print_details(); int total=Account.read_count(); Console.WriteLine("no of Accounts:{0}",total);

}}


26



Total no of Accounts:2


27

Q71. Complete the following class & main menu

class Time{ private int sec; private int min; public Time(int m, int s){ ….. public void increment_sec(){ …. public void print_time(){ …..

}

public class Q71{public static void Main(){…

Note: Sec ==60?


28


class Item{private int lotno;private String bidder;private int bid;

public Item(int l,String bn, int b){...public void nextbid(String b_name, int amt){...public void print_details(){ }}

public class Q72{public static void Main(){…

Note: next bid only accepted if > current bid

Online Auction


29

Now Version 3:

Inheritance

class Counter{ protected int value; private string name;

public Counter(int v, String n){ this.value = v; this.name = n;}

public void increment(){this.value++;}

public int read_value(){ return this.value;}

}

class MyCounter : Counter{ private char sign;

public MyCounter(int v, String n, char s):base(v,n){ this.sign = s;}

public void decrement() {this.value--;}

new public int read_value(){ if (this.sign=='-') return this.value * -1;

else return this.value;}

public void change_sign(){ if (this.sign=='-') this.sign = '+';

else this.sign = '-';}}

public class Ex1{public static void Main(){ MyCounter c1=new MyCounter(6,"Days Worked",'+'); int choice=0; while (choice !=4){

Console.WriteLine(":");Console.WriteLine("1: Increment");Console.WriteLine("2: Decrement");Console.WriteLine("3: Read Value");Console.WriteLine("4: Exit");Console.Write("Enter Choice: ");string temp=Console.ReadLine();choice=Convert.ToInt32(temp);switch(choice){

case 1: c1.increment(); break;case 2: c1.decrement(); break;case 3: int res=c1.read_value(); Console.WriteLine(": {0}",res); break;}}}}

class Account{ private int accNo; protected int balance; public Account(int No, int bal){ this.balance=bal;

this.accNo=No;}public int getAccNo(){return accNo;}



public void print_details(){ Console.Write("Details"+ ":"); Console.WriteLine("{0} Balance: {1}",accNo,balance);}}


34

class ATMaccount: Account{ private int pin;public ATMaccount(int n,int bal, int pin):base(n,bal)

{this.pin=pin;}

public bool debit(int amount){ if (amount > balance) return false;

else { balance = balance - amount; return true;}}

public bool pinOK(int pin){ if (this.pin==pin) return true;

else return false;}

new public void print_details(){ base.print_details(); Console.WriteLine("Pin: {0}",pin);}

}


35

public class Ex1{

public static void Main(){ ATMaccount a1 = new ATMaccount(3214, 100, 2222); Console.Write("Enter Pin"); int pin=Convert.ToInt32(Console.ReadLine()); while (a1.pinOK(pin)==false) { Console.Write("Enter Pin"); pin=Convert.ToInt32(Console.ReadLine());}

int amt=0, choice=0; :


36

:while (choice !=4){

Console.WriteLine(":");Console.WriteLine("1: Deposit");Console.WriteLine("2: Withdraw");Console.WriteLine("3: Check Balance");Console.WriteLine("4: Exit");Console.Write("Enter Choice:");

choice=Convert.ToInt32(Console.ReadLine());switch(choice){ case 1: Console.Write("Enter Amount: ");

amt=Convert.ToInt32(Console.ReadLine()); a1.credit(amt); break;

case 2: Console.Write("Enter Amount: "); amt=Convert.ToInt32(Console.ReadLine());

a1.debit(amt); break; case 3: a1.print_details(); break;

}}}}


37


38

Section 1


(Revision)


39

class LList{private int[] list;private int count;private int size;


this.list=new int[s];}

public void insert(int v){ if (count<size){

list[count]=v; count++;}}:


40

:

public void print_LList(){ Console.WriteLine("");

for(int i=0;i<count;i++){ Console.WriteLine(" {0}",list[i]);

}}

}


41

public class Ex1{

public static void Main(){ LList s = new LList(5);

int val=0, choice=0;while (choice !=3){

Console.WriteLine(":");Console.WriteLine("1: Insert");Console.WriteLine("2: Print Stack");Console.WriteLine("3: Exit"); :


42

:Console.Write("Enter Choice:");

choice=Convert.ToInt32(Console.ReadLine());

switch(choice){ case 1: Console.Write("Enter Value");

val=Convert.ToInt32(Console.ReadLine()); s.insert(val); break;



43

class LList{protected int[] list;protected int count;private int size;


this.list=new int[s];} public void insert(int v){ if (count<size){

list[count]=v; count++;}}

public void print_LList(){:


44

class Stack : LList{

public Stack(int s):base(s){}

public int remove(int v){ int res=-1;

if (count >0){ res=list[count-1]; count--;}

return res; }

}


45

public class Ex1{

public static void Main(){ Stack s = new Stack(5); int val=0, choice=0; while (choice !=4){ Console.WriteLine(":"); Console.WriteLine("1: Insert"); Console.WriteLine("2: Remove"); Console.WriteLine("3: Print Stack"); Console.WriteLine("4: Exit");

Console.Write("Enter Choice:"); choice=Convert.ToInt32(Console.ReadLine()); :


46

: switch(choice){

case 1: Console.Write("Enter Value"); val=Convert.ToInt32(Console.ReadLine());

s.insert(val); break; case 2: val=s.remove(val); if (val>=0)

Console.Write("{0} Deleted",val); break;



47


class MyTime : Time

1- additional parameter ‘hour’

2. Modified functions - increment_sec() - print_time()

3. New function - increment_hour()

Note: ‘protected’ data


48


class Exp_Item : Item{ // bid only accepted if > limit also

1- additional parameter ‘limit’

2. Modified functions - nextbid(String b_name, int amt)

- print_details()

3. New function - set_limit(int l)

Note: ‘protected’ data


49

Next Version4: Polymorphism

(Dynamic Binding)


50

class Base{ public void f1() {Console.WriteLine("f1 base");} public virtual void f2() {Console.WriteLine("f2 base");}}class Derv: Base{

new public void f1() {Console.WriteLine("f1 derv");} public override void f2() {Console.WriteLine("f2 derv");}}


51

public class Ex1{

public static void Main(){Base b=new Base();b.f1();b.f2();Console.Read();

}}


52


53

public class Ex1{

public static void Main(){Base b=new Derv();b.f1();b.f2();Console.Read();

}}


54


55

class Account{ private int accNo; protected int balance; public Account(int No, int bal){ this.balance=bal;

this.accNo=No;}public int getAccNo(){return accNo;}public int getBalance() {return balance;}public void credit(int amount){ balance+=amount;}public virtual bool pinOK(int pin){return true;}

public virtual bool debit(int amount){ return true;}

public virtual void print_details(){ Console.Write("Details"+ ":"); Console.WriteLine("{0} Balance: {1}",accNo,balance);}} :

}


56


{this.pin=pin;} public override bool debit(int amount){

Console.WriteLine("derv"); if (amount > balance) return false; else { balance = balance - amount;

return true;}} public override bool pinOK(int pin){

if (this.pin==pin) return true; else return false;}public override void print_details(){ base.print_details(); Console.WriteLine("Pin: {0}",pin);}

}


57

public class Ex1{public static void Main(){ Account a1 = new ATMaccount(3214, 100, 2222); Console.Write("Enter Pin"); int pin=Convert.ToInt32(Console.ReadLine()); while (a1.pinOK(pin)==false) { Console.Write("Enter Pin"); pin=Convert.ToInt32(Console.ReadLine());} int amt=0, choice=0; while (choice !=4){ :


58

:switch(choice){


a1.credit(amt); break;


a1.debit(amt); break;

case 3: a1.print_details(); break;}}}}


59

public class Ex2{

public static void Main(){ Account[] array = new Account[2];

array[0] = new ATMaccount(3210,100,2222); array[1] = new Account(3211,200); if (array[0].pinOK(2222)==true){

array[0].credit(50); } for(int i=0; i<2;i++)

{array[i].print_details();} }

}


60

Account DetailsNo:1 Balance:150Pin: 2222



61

Version 5:

Abstract Classes


62

abstract class Account{ private int accNo; protected int balance;

public Account(int No, int bal){ this.balance=bal; this.accNo=No;}

public int getAccNo(){return accNo;}


public void credit(int amount){ balance+=amount;} public abstract bool pinOK(int pin);

public abstract bool debit(int amount); :}

abstract classes & interfaces


63


{this.pin=pin;} public override bool debit(int amount){

Console.WriteLine("derv"); if (amount > balance) return false; else { balance = balance - amount;

return true;}} public override bool pinOK(int pin){

if (this.pin==pin) return true; else return false;}public override void print_details(){ base.print_details(); Console.WriteLine("Pin: {0}",pin);}

}


64

public class Ex2{

public static void Main(){ Account[] array = new Account[2];

array[0] = new ATMaccount(3210,100,2222); array[1] = new ATMaccount(3211,200,3333); if (array[0].pinOK(2222)==true){

array[0].credit(50); } for(int i=0; i<2;i++)

{array[i].print_details();} }

}


65



pure abstract class

abstract class Counter{

public abstract void increment();

public abstract void decrement();

public abstract int read_value();}

class MyCounter : Counter{ private int value; private String name; private char sign; public MyCounter(int v, String n, char s) { this.value = v;

this.name = n;this.sign = s;}

public override void decrement() {this.value--;} public override void increment(){this.value++;} public override int read_value(){ if (this.sign=='-') return this.value * -1;

else return this.value;} public void change_sign(){ if (this.sign=='-') this.sign = '+';



Console.WriteLine(":");Console.WriteLine("1: Increment");Console.WriteLine("2: Decrement");Console.WriteLine("3: Read Value");Console.WriteLine("4: Exit");Console.Write("Enter Choice: ");string temp=Console.ReadLine();

choice=Convert.ToInt32(temp);switch(choice){ case 1: c1.increment(); break; case 2: c1.decrement(); break; case 3: int res=c1.read_value(); Console.WriteLine(": {0}",res); break;}}

}}

interfaces

interface Counter{

void increment();

void decrement();

int read_value();}


72

class MyCounter : Counter{ private int value; private String name; private char sign; public MyCounter(int v, String n, char s) { this.value = v;

this.name = n;this.sign = s;}

public void decrement() {this.value--;} public void increment(){this.value++;} public int read_value(){ if (this.sign=='-') return this.value * -1;

else return this.value;} public void change_sign(){ if (this.sign=='-') this.sign = '+';



73


Console.WriteLine(":");Console.WriteLine("1: Increment");Console.WriteLine("2: Decrement");Console.WriteLine("3: Read Value");Console.WriteLine("4: Exit");Console.Write("Enter Choice: ");string temp=Console.ReadLine();

choice=Convert.ToInt32(temp);switch(choice){ case 1: c1.increment(); break; case 2: c1.decrement(); break; case 3: int res=c1.read_value(); Console.WriteLine(": {0}",res); break;}}

}}


74

interface X{void f0();

}class Base{

public void f1(){Console.WriteLine("f1 base");}

public virtual void f2(){Console.WriteLine("f2 base");}}

class Derv: Base,X{ new public void f1(){Console.WriteLine("f1 derv");}

public override void f2(){Console.WriteLine("f2 derv");} public void f0(){Console.WriteLine("f interface");}}}}


75

<< abstract>>Counter

protected int value

Counter (int v){abstract} void increment(){abstract} void decrement()double read_val();

Step_by_one

void increment() // step value up by 1void decrement() // step down by 1

Step_by_two

void increment() // step value up by 2void decrement() // step down by 2

Q75. Using the following class diagram as a basis outline a complete application which demonstrates how an ‘abstract’ class is defined and used in java.

Use the following Test Fn


76

public class Q75{ public static void main(String[] args){ Counter[] c1=new Counter[2];

Steps_of_one s1=new Steps_of_one(5); Steps_of_two s2=new Steps_of_two(5); c1[0]=s1; c1[1]=s2;

int choice=0, index=0;while (choice!=4){Console.WriteLine(":");Console.WriteLine("1: Increment");Console.WriteLine("2: Decrement");Console.WriteLine("3: Read Value");Console.WriteLine("4: Exit");Console.Write("Enter Choice: ");string temp=Console.ReadLine();

choice=Convert.ToInt32(temp); Console.Write(" Enter Counter Index (0 or 1:");

string temp1=Console.ReadLine(); choice=Convert.ToInt32(temp1);

switch(choice){case 1: c1[index].increment(); break;case 2: c1[index].decrement(); break;case 3: System.out.println("Value= "+ c1[index].readvalue()); break;}

} }}


77

Q76. Using the following class diagram as a basis outline a complete application which demonstrates how an ‘interface’ is defined and used in java.

<< interface>>Counter

void increment()void decrement()double read_val();

FloatCounter

float value;


DoubleCounter

double value;



78

Now Back to First Program

We will introduce a different form of Error Handling

Exception Handling


this.accNo=No;}


public bool debit(int amount){ if (amount > balance) return false;

else { balance = balance - amount;return true;}}

public void print_details(){ Console.Write("Details"+ ":"); Console.WriteLine("{0} Balance: {1}",accNo,balance);}}


80

public class Ex1{

public static void Main(){ Account a1 = new Account(1,100);

Account a2 = new Account(2,200); a1.credit(50); bool res1=a2.debit( 50); if (res1==false){Console.WriteLine("Error"); } a1.print_details(); a2.print_details(); }}


81

class MyException:Exception{public MyException(string s):base(s){}public MyException():base(){}

}

Exception Handling


82


this.accNo=No;}

public void credit(int amount){ balance+= amount;}

public void debit(int amount){ if (amount > balance) throw new MyException();

else { balance = balance - amount;} }

:}


83

public class Ex1{

public static void Main(){ Account a1 = new Account(1,100);

Account a2 = new Account(2,200); a1.credit(50); try{ a2.debit( 450);} catch(Exception e){Console.WriteLine("Error"); } a1.print_details(); a2.print_details(); Console.Read();}}


84

Error




85

class Item{ private int lotno; private String bidder; private int bid;

public Item(int l,String bn, int b){lotno=l; bidder=bn; bid=b;}

public bool nextbid(String b_name, int amt){if (amt> bid){ bidder=b_name; bid=amt;

return true;}else return false;}

public void print_details(){ Console.WriteLine("Details:"); Console.WriteLine("Lot No: "+lotno); Console.WriteLine("Bidder Name:"+ bidder); Console.WriteLine("Bit Amount: "+ bid); } }

Q77. This Ex uses traditionalError Handling

-Rewrite usingExceptions

Continued…..


86

public class Q77{ public static void Main

Item item1=new Item(101,"NOBODY",0);int choice=1,amt;string name=" ";while (choice!=3){

Console.WriteLine("Menu:"); Console.WriteLine("1: Enter new Bid:"); Console.WriteLine("2: print Bid details:"); Console.WriteLine("3: Exit:");


87

Console.Write ("Enter Choice:"); string temp=Console.ReadLine();

choice=Convert.ToInt32(temp1);

switch(choice){ case 1: Console.Write ("Enter Amount:");

string temp1=Console.ReadLine(); amt=Convert.ToInt32(temp1);

Console.Write ("Enter Name:"); string name=Console.ReadLine(); bool res= item1.nextbid(name,amt); if (res==false) Console.Write ("Error Bid Too Low"); else Console.Write ln("Bid Accepted"); break;

case 2: item1.print_details(); break; case 3: break;}}}}


88

Aggregation


89

class Counter{ private int value;

public Counter(int v){ this.value = v;}public void update(int n)

{value=n;}public int read_value()

{ return this.value;}}


90

class Account{ protected Counter number; protected int balance; public Account(int n, int b){ number=new Counter(n);

balance=b;} public void update_number(int x){number.update(x);} public Counter read_num(){return number;} public void deposit(int amt) {this.balance+=amt;}

public void print(){ Console.Write("\nNo: {0}",number.read_value()); Console.WriteLine("Bal: {0}",balance);}

}


91

public class Ex1{

public static void Main(){ Account a1=new Account(10,100);

Account a2=new Account(20,200); a2.deposit(1); a2.print(); a1.update_number(30); a2.print();}

}


92

No: 20 Bal: 201

No: 30 Bal: 201


93

Aggregation

class Height {

private int feet, inches;

public Height( int f, int i ) { feet=f; inches = I;}

public int height_in_inches() { return (inches + feet*12); }

public void print(){

Console.Write(feet+”{0}\’-{1}\””,feet, inches);}

}


94

class Student {

private int age;

private String name;

private Height ht;

public Student( int a, String n, int f, int i )

{ht=new Height(f,i);

age=a; name=n; }

public void increment_age() { return age++; }


Console.Write (“Age:{0}\nName: {1}“,age, name;}

Console.Write (“\nHeight:”);

ht.print(); }

}


95

public class Test {


Student s1=new Student(20, “J.Smith”, 5,11);

int result = s1.read_height_in_inches();

Console.WriteLine(“Height in ins:{0}”, result);

s1.print();

}


96

Association


97

class Counter{ private int value;

public Counter(int v){ this.value = v;}public void update(int n)

{value=n;}public int read_value()

{ return this.value;}}


98

class Account{ protected Counter number; protected int balance; public Account(Counter no, int b){ number=no;

balance=b;} public void update_number(int x){number.update(x);} public Counter read_num(){return number;} public void deposit(int amt) {this.balance+=amt;} public void print(){

Console.Write("\nNo: {0}",number.read_value()); Console.WriteLine("Bal: {0}",balance);}

}


99

public class Ex21{

public static void Main(){ Counter c1=new Counter(10); Counter c2=new Counter(20);

Account a1=new Account(c1,100); Account a2=new Account(c2,200); a2.deposit(1); a2.print(); a1.update_number(30); a2.print();}

}


100

No: 20 Bal: 201

No: 30 Bal: 201


101

Association

class Height {



public Height( ) { feet = 0; inches=i; }

public Height( Height h ){ feet= h.feet; inches= h.inches }



Console.Write(feet+”{0}\’-{1}\””,feet, inches);}

}


102

class Student {

private int age;


private Height ht;

public Student( int a, String n, Height h )

{age=a; name=n; ht=h;}

public int read_height_in_inches() { return ht.height_in_inches(); }


Console.Write (“Age:{0}\nName: {1}“,age, name;}

Console.Write (“\nHeight:”);

ht.print(); }

}


103

public class Test {


Height h1=new Height(5,11);

Student s1=new Student(20, “J.Smith”, h1);


System.out.println(“Height in ins:”+result);

s1.print();

}


104

class Money{private int euro,cent;public Money(int e, int c){ this.euro=e; this.cent=c;}public void print(){ Console.WriteLine("E{0}.{1}"euro,cent);}public void reset(int x, int y){ euro=x; cent=y;}public boolean greater(int x, int y){ int val1_in_cent= y+x*100; int val2_in_cent= cent+euro*100;

if (val1_in_cent > val2_in_cent) return true;else return false;}

}

class Item{private int lotno;private String bidder;private Money bid;

Q78. Complete the following as an example of Aggregation

Continued…..


105

public class Q78{

public static void main(String[] args){Item item1=new Item(101,"NOBODY",0,0);int choice=1,amt1,amt2; String name=new String(" ");while (choice!=3){

System.out.println("Menu:");System.out.println("1: Enter new Bid:");System.out.println("2: print Bid details:");System.out.println("3: Exit:");choice=Console.readInt("Enter Choice:");switch(choice){

case 1: amt1=Console.readInt("Enter Amount in Euro:"); amt2=Console.readInt("Enter Amount in Cent:"); name=Console.readLine("Enter Name of bidder: "); try {item1.nextbid(name,amt1,amt2);

System.out.println("Bid Accepted");} catch(Exception e){ System.out.println("Error Bid Too Low");} break;

case 2: item1.print_details(); break;}}}}


106

class Money{private int euro,cent;public Money(int e, int c){ this.euro=e; this.cent=c;}public void print(){ System.out.println("E"+euro+"."+cent);}public void reset(int x, int y){ euro=x; cent=y;}public boolean greater(int x, int y){ int val1_in_cent= y+x*100; int val2_in_cent= cent+euro*100;

if (val1_in_cent > val2_in_cent) return true;else return false;}

}

class Item{private int lotno;private String bidder;private Money bid;

Q79. Now rewrite as an example of Association


107

Operator Overload


108

class Rational{ private int num, den; public Rational(){} public Rational(int n, int d){

this.num = n; this.den =d;} public static double translate(Rational r1){ return (double) r1.num/r1.den;} public static Rational mult(Rational r1, Rational r2)

{ Rational res=new Rational(); res.num= r1.num*r2.num; res.den= r1.den*r2.den;

return res;}public void print(){

Console.WriteLine("{0}/{1}",num,den); }}


109

public class Ex1{

public static void Main(){ Rational r1=new Rational(2,3); Rational r2=new Rational(1,2); Rational res1=Rational.mult(r1,r2); Console.Write("Result of mult: "); res1.print(); double res2=Rational.translate(r2); Console.Write("Result of Translation:{0}",res2); Console.Read();}

}


110


111

Now we will rewrite using

Operator Overload


112

class Rational{ private int num, den; public Rational(){} public Rational(int n, int d){

this.num = n; this.den =d;} public static explicit operator double (Rational r1) {return (double) r1.num/r1.den;} public static Rational operator*(Rational r1, Rational r2)

{ Rational res=new Rational(); res.num= r1.num*r2.num; res.den= r1.den*r2.den; return res;}

public void print(){Console.WriteLine("{0}/{1}",num,den); }

}


113

public class Ex1{

public static void Main(){ Rational r1=new Rational(2,3); Rational r2=new Rational(1,2); Rational res1=r1 * r2; Console.Write("Result of mult: "); res1.print(); double res2=(double) r2; Console.Write("Result of Translation:{0}",res2); Console.Read();}

}


114

: Rational res1=r1 * r2; Console.Write("Result of mult: "); res1.print();

:

Now to handle printing


115

class Rational{ private int num, den; :public static implicit operator float (Rational r1) {return (float) r1.num/r1.den;}

}


116

public class Ex1{

public static void Main(){Rational r1=new Rational(2,3); Rational r2=new Rational(1,2); Rational res1=r1 * r2; Console.Write("Result of mult: {0}", res1);

:


117

Create a complex number class with real and imagineryParts.

Include opeartor overload for * and +

Plus implicit and implicit casting

Q710. CompleX Numbers


118

Section 8 - UML Static Modelling

Section 8.1 Class Diagrams


119

The Class Diagram

Classname ORClassname

attribute: datatype

operation(args: type): type


120

The Class Diagram

Software

Course

Book

Details

Author

1 0..*

0..*

1..*


121

Finding Classes

• Use domain analysis as before

• Derive them from the use cases

• Look for data which must be stored or analyzed

• Are there external systems?

• Are there any devices under the control of the system?

• Are there any organizational parts?


122

Attributes

• Describe the state & characteristics of the object

• Must be typed, primitives like integers:– Real

– Boolean

– Point

– String

• Visibility must be: public (+),

private (-),

protected (#)


123

Example UML Class

Invoice

+ amount: Real+ date: Date=Current_date+ customer: String+ specification: String- administration: String=“unspecified”- number_of_invoices: Integer+ status: Status=unpaid {paid, unpaid}

Name, bold

Public, typed

Default value

Private

Class variable

property


124

Associations

Associations model Class relationships Associations should be named Use verbs from the problem domain Roles played by classes may also be named Associations have a cardinality


125

Association • One player may be a member of many teams

(United & Ireland)

•Player may leave one team & join another

TeamPlayer

**


126

Associations & Cardinality

Exactly One (default)

Zero or more

Optional (zero or one)

One or more

Numerically specified

Class1 Class1

Class

Class

Class

Class

Class

Association Name

*

0..1

1..*

3..8


127

Cardinality Examples

Employee

Name:String

Number:Integer

Dept

Name:String

VideoMember

Association Name

0..1 Rent *

HiresCustomer

Car

Reg: String

year: Integer


128

Class & Object Representation

Tsmith:Member

SpaceBalls: Video

VideoMember 0..1 Rent *

Rocky: Video


129

Association example

Insurance Policy

Insurance Contract

1 owns 0..*

refers to

Insurance

company

Customer

0..1

is expressed in

1

expresses an

has

0..1

refers to

1..* Note: Insurance Policy sent

after contract agreed


130

Association example expanded

Insurance Policy

Insurance Contract 1 owns 0..*

refers to

Insurance

company

Person

0..1

is expressed in

1

expresses an

has

0..1

refers to

1..*

husbandwife

Married to

insurer


131

Aggregation & Composition

• Special type of association

– “consists of”

– “contains”

– “part of”


132

Employee

Contract Aggregation

0..1 Delivery_Van

reg:String


133

Car

Service_record Aggregation

Owner

name:String


134

JFrame

TextField*

Listbox*

Button*

MenuItem*


135

Section 8.1 Exercises

8.1.1 Draw a Class Diagram for a company that employs many people. For each association between company and employee their is a contract.

The company has many divisions and each division has many departments. At any time an employee will be allocated to one department.


136

8.1.2

Outline a UML class that models the following proposed system. Make any assumptions you think appropriate. Include details of suitable attributes & methods.

“A boss/owner of a small retail outlet wants a computer system to automatehis admin procedures. He wants to record details about each employee, theirindividual employment contracts, employee sales records and details of the company cars some employees are supplied with. Details concerning allsuppliers and customers must also be recorded and a separate account ismaintained per customer. Its also necessary to keep track of all items in stock and the accounts for the company in general”.


137

Static Modelling 8.2

Section 8.2

Inheritance


138

Example

CarGeneral

Estate CoupeHatchbackSaloonSpecific


139

Java Implementation

Account

#amt:Real

+deposit()

ATMAccount

-pin:Integer

+withdraw()


140

Subclasses and Inheritance

class Account{

protected double amt;

public Account(int a) { }

:

} public class ATMAccount extends Account {

private int pin;

:

public void withdraw( int a) { amt = amt - a; } }


141

Concrete Subclasses

Car {abstract}

Estate CoupeHatchbackSaloon


142

Polymorphism

Shape

#colour:Colour

Draw(){abstract}

Square

Draw()

Circle

Draw()


143

Ways of showing constraints

Class A

Class B Class C Class D

{constraint 1,

constraint2}

Class A

Class B Class C Class D

{constraint 1,

constraint2}


144

Constrained Generalisation

• Generalisation may be:– Overlapping: a subclass can inherit from 2 classes, each of

which has a common parent

– Disjoint: opposite (default)

– Complete: no further class can inherit from this superclass

except those just specified

– Incomplete (default)


145

Overlapping Inheritance

Vehicle

Boat Car

Hovercraft

{overlapping}


146

Complete Inheritance

Person

Woman Man

{complete}

• No further class may inherit from Person in future


147

Exercises - Section 7.2

Ex8.2.1 Outline an Object Class Diagram for the following:

A company owns many computers. A company employs many employees. Most employees works on the same computer all the time. A few employees don’t use a computer at all.

The company has 2 types of computer: IBM and Apple. Some of the IBMs have Multimedia capability.


148

Ex7.2.2Using the UML methodology outline a Class Diagram that models the Banking System detailed below. Add attributes, operations, aggregations and associations as appropriate. Add additional classes as needed.

Can assume the Bank consists of Customer Accounts and an object describing the bank’s own finances.

These Customer Accounts can be of a General type or may be some sort of special Accounts with some additional parameters (e.g. Joint, Savings Account etc).Each Account is associated with a Customer object outlining customer details.

Each Customer may have more than one Account.


149

Ex7.2.3A company administration system records details concerning Employee detailsincluding name, number, salary, age etc. Employees are classified into various groups (Managers, Craftsmen etc) for administration purposes.Operations on Employees typically updates details like age and salary etc.Each employee has a contact. Work is organised into Projects, each projectHas a single manager but several workers in other categories. An employeecan be allocated to a maximum of two projects.

Using this application, adding more details to the requirements as needed, describe in detail the complete UML Class Diagram.


150

Appendix 1- Chapter 7

Aggregation & Association


151

Aggregation

class Height {






public void print(){ System.out.print(feet+”’-”+inches+”\” ”);}

}


152

class Student {

private int age;


private Height ht;

public Student( int a, String n, int f, int i )

{ht=new Height(f,i);

age=a; name=n; }



System.out.print(“Age:”+age + “\nName: “+ name;}

System.out.print(“\nHeight:”);

ht.print(); }

}


153

public class Test {

public static void main(String[] args){

Student s1=new Student(20, “J.Smith”, 5,11);



s1.print();

}


154

Association

class Height {






public void print(){ System.out.print(feet+”’-”+inches+”\” ”);}

}


155

class Student {

private int age;


private Height ht;

public Student( int a, String n, Height h )

{age=a; name=n; ht=h;}



System.out.print(“Age:”+age + “\nName: “+ name;}

System.out.print(“\nHeight:”);

ht.print(); }

}


156

public class Test {


Height h1=new Height(5,11);

Student s1=new Student(20, “J.Smith”, h1);



s1.print();

}


157

Appendix 2 - Abstract Class

In it will now look at 4 versions of the same program:

1) Normal Inheritance

2) abstract function

3) abstract class

4) interface

See Appendix 1 - Additional Examples


158

class Rat{ // Version 1 -Normal Inheritance

protected int num, den;

public Rat(int n, int d){num=n; den=d;}

public int readnum() {return num;}

public void print() {System.out.println("Rat: "+num+"/"+den);}

}

class RatSign extends Rat {

private char sign;

RatSign(char s, int n, int d){ super(n,d); sign=s;}

public int readden(){return den;}

public void print(){System.out.println(sign+num+"/"+den);}

}


159

public class Version1{


Rat rArray[] = new Rat[2];

Rat r = new Rat(2,3);

RatSign rs = new RatSign('-', 3, 4);

rArray[0] = r;

rArray[1] = rs;

for( int i = 0; i < rArray.length; i++ )

rArray[i].print();

}

}


160

abstract class Rat{ // Version 2: Abstract function

protected int num, den;

public Rat(int n, int d){num=n; den=d;}

public int readnum() {return num;}

abstract public void print();

}


private char sign;

RatSign(char s, int n, int d){ super(n,d); sign=s;}



}


161




// Rat r = new Rat(2,3); - not allowed RatSign rs2 = new RatSign('+',2,3);


rArray[0] = rs2;

rArray[1] = rs;


rArray[i].print();

}

}


162

abstract class Rat{ // Version 3: abstract class

abstract public int readnum();

abstract public void print();

}


private int num, den;

private char sign;

RatSign(char s, int n, int d){ num=n; den=d; sign=s;}

public int readnum(){return num;}



}


163




RatSign rs2 = new RatSign('+',2,3);


rArray[0] = rs2;

rArray[1] = rs;


rArray[i].print();

}

}


164

interface Rat{ // Version 4: interface

public int readnum();

public void print();

}

class RatSign implements Rat {

private int num, den;

private char sign;

RatSign(char s, int n, int d){ num=n; den=d; sign=s;}

public int readnum(){return num;}



}


165




RatSign rs2 = new RatSign('+',2,3);


rArray[0] = rs2;

rArray[1] = rs;


rArray[i].print();

}

}

Another Example- Interface

• public interface Value { public void setValue( float c ); public float readValue(); public void printValue( ); }

• public class Intvalue implements Value { private int val; public void setValue( float c ){val=(float) c;} public float readValue(){return val;} public void printValue( )

{ System.out.print(“Value:” + val);}

}


167

Defining an Interface• public class Floatvalue implements Value {

private float val;

public void setValue( float c ){val= c;} public float readValue(){return val;} public void printValue( ) {System.out.print(“Val:” + val);} }

• public class Test{


Value[] values = new Value[2]; values[0]=new Intvalue(); values[1]=new Floatvalue() ); for( int i = 0; i < values.length; i++ ) { values[i].setValue(i+2);

values[i].printValue();}} }

sep 2005 sdp-msc slide 1 section 7 object oriented programming

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