CMSC 132, Object-Oriented Programming II Summer Lecture 1:

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1 CMSC 132, Object-Oriented Programming II Summer 2016 Lecturer: Anwar Mamat Lecture 1: Disclaimer: These notes may be distributed outside this class only with the permission of the Instructor. 1.1 Course Introduction Check the course website for the syllabus and course introduction slides. 1.2 Java Review We start by introducing Object Oriented Programming (OOP) concepts, such as class, inheritance, and encapsulation Code Examples: Fraction Class In this example, we implement a Fraction class, which can represent fractions and support arithmetic operations on the fractions. A common fraction consists of an integer numerator, and non-zero denominator For example: 10 or 5. The Fraction class has two private members numerator and denominator. Listing 1: Fraction Class 1 / 2 Fraction c l a s s implements non n e g a t i v e f r a c t i o n s anwar 4 / 5 public class Fraction { 6 protected int numerator ; 7 protected int denominator ; 8 / Constructs a Fraction n/d. n i s the numerator, assumed non n e g a t i v e. d i s t he denominator, assumed p o s i t i v e. 11 / 12 Fraction ( int n, int d ) { 13 int g = gcd (d, n ) ; 14 / reduce the f r a c t i o n / 15 numerator = n/ g ; 16 denominator = d/ g ; 17 } / Constructs a Fraction n /1. n i s the numerator, assumed non n e g a t i v e. 21 / 1-1

2 1-2 Lecture 1: 22 public Fraction ( int n ) { 23 this (n, 1 ) ; 24 } / Constructs a Fraction 0/1. 27 / 28 public Fraction ( ) { 29 numerator = 0 ; 30 denominator = 1 ; 31 } public S t r i n g t o S t r i n g ( ) { 34 return ( numerator + / + denominator ) ; 35 } / C a l c u l a t e s and r e t u r n s the double f l o a t i n g p o i n t v a l u e o f a f r a c t i o n. a double f l o a t i n g p o i n t v a l u e f o r t h i s Fraction. 39 / 40 public double e v a l u a t e ( ) { 41 double n = numerator ; // convert to double 42 double d = denominator ; 43 return ( n / d ) ; 44 } / Add f 2 to t h i s f r a c t i o n and return the r e s u l t. f 2 i s the f r a c t i o n to be added. the r e s u l t o f adding f 2 to t h i s Fraction. 49 / 50 public Fraction add ( Fraction f 2 ) { 51 Fraction r = new Fraction ( ( numerator f 2. denominator ) + 52 ( f 2. numerator denominator ), 53 ( denominator f 2. denominator ) ) ; 54 return r ; 55 } / s u b t r a c t f 2 from t h i s f r a c t i o n and return the r e s u l t. f 2 i s the f r a c t i o n to be added. the r e s u l t o f adding f 2 to t h i s Fraction. 60 / 61 public Fraction sub ( Fraction f 2 ) { 62 Fraction r = new Fraction ( ( numerator f 2. denominator ) 63 ( f 2. numerator denominator ), 64 ( denominator f 2. denominator ) ) ; 65 return r ; 66 } / m u l t i p l e f 2 to t h i s f r a c t i o n and return the r e s u l t. f 2 i s the f r a c t i o n to be added. the r e s u l t o f adding f 2 to t h i s Fraction. 71 / 72 public Fraction mul ( Fraction f 2 ) {

3 Lecture 1: return ( 74 new Fraction ( numerator f 2. numerator, 75 denominator f 2. denominator ) 76 ) ; 77 } / d i v i d e f 2 to t h i s f r a c t i o n and return the r e s u l t. f 2 i s the f r a c t i o n to be added. the r e s u l t o f adding f 2 to t h i s Fraction. 82 / 83 public Fraction div ( Fraction f 2 ) { 84 return ( 85 new Fraction ( numerator f 2. denominator, 86 denominator f 2. numerator ) 87 ) ; 88 } / Computes the g r e a t e s t common d i v i s o r ( gcd ) o f the two i n p u t s. a i s assumed p o s i t i v e b i s assumed non n e g a t i v e the gcd o f a and b 94 / 95 static private int gcd ( int a, int b ) { 96 int t ; 97 // a must be g r e a t e r than or e q u a l to b 98 i f ( a < b ){ 99 t = a ; 100 a = b ; 101 b = t ; 102 } 103 i f ( b == 0){ 104 return a ; 105 } else { 106 return gcd (b, a%b ) ; 107 } 108 } public static void main ( S t r i n g [ ] argv ) { 111 / Test a l l t h r e e c o n t r u c t o r s and t o S t r i n g. / 112 Fraction f 0 = new Fraction ( ) ; 113 Fraction f 1 = new Fraction ( 3 ) ; 114 Fraction f 2 = new Fraction (12, 2 0 ) ; System. out. p r i n t l n ( \ ntesting c o n s t r u c t o r s ( and t o S t r i n g ) : ) ; 117 System. out. p r i n t l n ( The f r a c t i o n f 0 i s + f 0. t o S t r i n g ( ) ) ; 118 System. out. p r i n t l n ( The f r a c t i o n f 1 i s + f 1 ) ; // t o S t r i n g i s i m p l i c i t 119 System. out. p r i n t l n ( The f r a c t i o n f 2 i s + f 2 ) ; / Test methods on Fraction : add and e v a l u a t e. / 122 System. out. p r i n t l n ( \ ntesting add and e v a l u a t e : ) ; 123 System. out. p r i n t l n ( The f l o a t i n g point value o f + f 1 + i s +

4 1-4 Lecture 1: 124 f 1. e v a l u a t e ( ) ) ; 125 System. out. p r i n t l n ( The f l o a t i n g point value o f + f 2 + i s f 2. e v a l u a t e ( ) ) ; Fraction sumoftwo = f 1. add ( f 2 ) ; 129 Fraction sumofthree = f 0. add ( f 1. add ( f 2 ) ) ; System. out. p r i n t l n ( The sum o f + f 1 + and + f 2 + i s + sumoftwo ) ; 132 System. out. p r i n t l n ( The sum o f + f 0 +, + f 1 + and + f 2 + i s sumofthree ) ; 134 / 135 t e s t sub, div, mul here 136 / 137 / Test gcd f u n c t i o n ( s t a t i c method ). / 138 System. out. p r i n t l n ( \ ntesting gcd : ) ; 139 System. out. p r i n t l n ( The gcd o f 2 and 10 i s : + gcd ( 2, 1 0 ) ) ; 140 System. out. p r i n t l n ( The gcd o f 15 and 5 i s : + gcd (15, 5 ) ) ; 141 System. out. p r i n t l n ( The gcd o f 24 and 18 i s : + gcd (24, 1 8 ) ) ; 142 System. out. p r i n t l n ( The gcd o f 10 and 10 i s : + gcd (10, 1 0 ) ) ; 143 System. out. p r i n t l n ( The gcd o f 21 and 400 i s : + gcd (21, ) ) ; 144 } 145 } MixedFraction inherits Fraction, so that it inherits addition, subtraction etc. Only difference is that mixed fraction is a whole number and a fraction combined. For example: = 13 5 Listing 2: MixedFraction Class 1 / 2 This c l a s s implements mixed f r a c t i o n anwar mamat 4 / 5 public class MixedFraction extends Fraction { 6 / Constructs a Fraction m n/d. m i s the i n t e g e r p a rt. n i s the numerator, assumed non n e g a t i v e. d i s t he denominator, assumed p o s i t i v e. 10 / 11 public MixedFraction ( int m, int n, int d ){ 12 super (m d+n, d ) ; // convert mixed f r a c t i o n i n t o proper f r a c t i o n. 13 } / Constructs a Fraction m n/d. f i s a f r a c t i o n 17 / 18 public MixedFraction ( Fraction f ) { 19 super ( f. numerator, f. denominator ) ; 20 } public S t r i n g t o S t r i n g ( ) { 23 int m = numerator / denominator ; 24 int n = numerator % denominator ;

5 Lecture 1: return (m + + n + / + denominator ) ; 26 } 27 } Main is the fraction test driver class. The main method of this class creates Fraction objects and prints the result in the console. Listing 3: Fraction Test Driver 1 public class Main{ 2 public static void main ( S t r i n g [ ] args ) { 3 Fraction f 1 = new Fraction ( 2, 1 0 ) ; 4 Fraction f 2 = new MixedFraction ( 1, 2, 1 0 ) ; 5 System. out. p r i n t l n ( f 1= + f 1 ) ; 6 System. out. p r i n t l n ( f 2 = + f 2 ) ; 7 MixedFraction f 3 = new MixedFraction ( f 2. add ( f 1 ) ) ; 8 System. out. p r i n t l n ( f f 2 + = + f 3 ) ; 9 Fraction f 4 = f 2. sub ( f 1 ) ; 10 System. out. p r i n t l n ( f f 1 + = + f 4 ) ; 11 Fraction f 5 = f 1. mul ( f 2 ) ; 12 System. out. p r i n t l n ( f f 2 + = + f 5 ) ; 13 Fraction f 6 = f 1. div ( f 2 ) ; 14 System. out. p r i n t l n ( f 1 + / + f 2 + = + f 6 ) ; 15 } 16 } We also create a JUnit test class for fraction. Listing 4: Fraction JUnit Test 1 2 import static org. j u n i t. Assert. ; 3 import org. j u n i t. Test ; 4 import org. j u n i t. After ; 5 import org. j u n i t. A f t e r C l a s s ; 6 import org. j u n i t. Before ; 7 import org. j u n i t. B e f o r e C l a s s ; 8 import org. j u n i t. Test ; 9 import static org. j u n i t. Assert. ; / 12 anwar 14 / 15 public class FractionTest { public FractionTest ( ) { 18 } public static void setupclass ( ) { 22 System. out. p r i n t l n ( UtilsJUnit4Test method ) ;

6 1-6 Lecture 1: 23 } public static void teardownclass ( ) { 27 System. out. p r i n t l n ( UtilsJUnit4Test method ) ; 28 } public void setupagain ( ) { 32 System. out. p r i n t l n ( UtilsJUnit4Test method ) ; 33 } public void teardown ( ) { 37 System. out. p r i n t l n ( UtilsJUnit4Test method ) ; 38 } 39 / 40 Test o f t o S t r i n g method, o f c l a s s Fraction. 41 / 43 public void t e s t T o S t r i n g ( ) { 44 System. out. p r i n t l n ( t o S t r i n g ) ; 45 Fraction i n s t a n c e = new Fraction ( 2, 1 0 ) ; 46 S t r i n g expresult = 1/5 ; 47 S t r i n g r e s u l t = i n s t a n c e. t o S t r i n g ( ) ; 48 a s s e r t E q u a l s ( expresult, r e s u l t ) ; 49 } 50 / 51 Test o f e v a l u a t e method, o f c l a s s Fraction. 52 / 54 public void t e s t E v a l u a t e ( ) { 55 System. out. p r i n t l n ( e v a l u a t e ) ; 56 Fraction i n s t a n c e = new Fraction ( 5, 1 0 ) ; 57 double expresult = 0. 5 ; 58 double r e s u l t = i n s t a n c e. e v a l u a t e ( ) ; 59 a s s e r t E q u a l s ( expresult, r e s u l t, 0. 0 ) ; 60 } / 63 Test o f add method, o f c l a s s Fraction. 64 / 66 public void testadd ( ) { 67 System. out. p r i n t l n ( add ) ; 68 Fraction f 2 = new Fraction ( 2, 7 ) ; 69 Fraction i n s t a n c e = new Fraction ( 1, 5 ) ; 70 Fraction expresult = new Fraction ( 1 7, 3 5 ) ; 71 Fraction r e s u l t = i n s t a n c e. add ( f 2 ) ; 72 a s s e r t E q u a l s ( expresult, r e s u l t ) ; 73 }

7 Lecture 1: / 76 Test o f sub method, o f c l a s s Fraction. 77 / 79 public void testsub ( ) { 80 System. out. p r i n t l n ( sub ) ; 81 Fraction f 2 = new Fraction ( 1, 5 ) ; 82 Fraction i n s t a n c e = new Fraction ( 4, 1 0 ) ; 83 Fraction expresult = new Fraction ( 1, 5 ) ; ; 84 Fraction r e s u l t = i n s t a n c e. sub ( f 2 ) ; 85 a s s e r t E q u a l s ( expresult, r e s u l t ) ; 86 } / 89 Test o f mul method, o f c l a s s Fraction. 90 / 92 public void testmul ( ) { 93 System. out. p r i n t l n ( mul ) ; 94 Fraction f 2 = new Fraction ( 3, 5 ) ; 95 Fraction i n s t a n c e = new Fraction ( 2, 3 ) ; 96 Fraction expresult = new Fraction ( 6, 1 5 ) ; 97 Fraction r e s u l t = i n s t a n c e. mul ( f 2 ) ; 98 a s s e r t E q u a l s ( expresult, r e s u l t ) ; 99 } / 102 Test o f d i v method, o f c l a s s Fraction. 103 / 105 public void t e s t D i v ( ) { 106 System. out. p r i n t l n ( div ) ; 107 Fraction f 2 = new Fraction ( 2, 5 ) ; 108 Fraction i n s t a n c e = new Fraction ( 3, 7 ) ; 109 Fraction expresult = new Fraction ( 1 5, 1 4 ) ; 110 Fraction r e s u l t = i n s t a n c e. div ( f 2 ) ; 111 a s s e r t E q u a l s ( expresult, r e s u l t ) ; 112 } }