Question

USING JAVA,

Class Design: Person The Person class is intended to be an abstract and simplified representation of a person. Each person will have an array of "friends" - which are other "Person" instances. Data to Store (2 Points) Name private instance variable with only private setter (2 Points) Friends private instance array with neither getter nor setter Actions Constructor o 1 Point) Take in as argument the name of the person (enforce invariants) o (1 Point) Initialize the array of friends to have at most 5 friends if you haven't done so already (2 Points) .equals() Override-compare another instance of a Person to determine whether it's the same person or not (what do you compare? How?) (2 Points) .toString() Override - return a String representation of this Person (what do you return?) . . Add Friend -take in as argument a "Person" instance. Some invariants: o (1 Point) Can't add self as friend o (1 Point) Don't add the same friend more than once. Hint: Use the .equals() method for Person (1 Point) Error checking: Handle the scenario if "Add Friend" is called when the array is "full" - what should happen? o . (2 Points) Add Friend overload take in as argument a "name" and create a Person object to add to the array of Friends. Enforce invariants. . (2 Points) Remove Friend - allow removing a friend - enforce invariants · (2 Points) List Friends-print out a list of friends (how is this different than having a "getter" for Friends?) . (+1 Bonus Point) Challenge: Automatically-growing array (zero bonus points if you use ArrayList) · (+2 Bonus Points) Challenge: Enforce “bilateral" relationships. I.e. Let's say "Person A" adds "Person B" as a friend. A "bilateral" relationship means that when "Person A" adds "Person B" as a friend, "Person B" also adds "Person A" as a friend. (Aside: What is a realistic model of real life relationships? Unilateral or bilateral?)

Answer 1

1 public class Person t 2 $ja Per pub 4 private Person friends; private String name; public Person String name) 10 12 setName(name); 13 14 friends new Person[5]; 15 16 17 18 19 20 private void setName(String name) £ 21 if (namenull I name.trimO.length0) 23 throw new IllegalArgumentException("Name cannot be null or blank"); 24 25 26 27 28 29 30 th'L . name name ; 32 34 35 36 eOverride 37 38 39 public boolean equals(Object o) if (o null && o instanceof Person) £

41 42 Person anotherPerson (Person) o; return anotherPerson.name.equalsIgnoreCase(this.name); 45 47 50 return false; 51 52 53 54 56 e0verride 57 58 public String toStringO 59 60 return "Name: " name; 62 63 64 65 public void addFriend(Person friend) [ 67 68 69 70 if(friend.name-name)t 71 72 System.out.println("You cannot be add yourself to the friend list." 73 74 return; 75 76 78 79 80 . for (int index - 0; index < friends.length; index++) I

82 83 if (friends index]-null) £ if (friends [index].equals(friend))5 85 86 87 System.out.println(friend.name+ " already exists"; return; 89 90 91 92 93 94 95 96 97 for (int index 0; index < friends.length; index++) I 98 100 if (friends index]null) £ 101 102 friends Cindex] friend; 103 104 return; 105 106 107 108 109 110 System.out.println( Error: Array already full"); 112 113 114 115 116 public void removeFriend(Person friend) 118 119 120

121 int size -0; 122 123 124 125 126 127 128 129 int index0fFriend 1; for (int index - 0; index < friends.length; index++) i if (friends index]- null) £ 130 131 size++; 132 133 134 break; 135 136 137 if (friends [index].name.equalsIgnoreCase(friend.name)) E 138 139 140 indexOfFriend index; 141 142 143 144 145 146 147 148 149 150 151 if (index0fFriend1 1 size0) return; if (index0fFriend size - 1) friends[indexOfFriend] null; 152 153 else £ 154 155 for (int indexindex0fFriend; index <- size - 2; index++) 156

156 157 for (int index = index0fFriend; index <= size - 2; index++) { $javac Person Person.java:4: public static 158 159 friends [index] friends [index 1]; 1 error 160 161 162 friends [size - 1] null; 163 164 165 166 167 168 169 170 public void addFriend(String name) 172 173 174 Person anotherPerson new Person(name); 175 176 addFriend(anotherPerson) 178 179 180 181 public void listFriendsO 182 183 184 System.out.println(" Friends of " name); 185 186 187 int friendCount-0 188 189 190 191 for (int index - 0; index < friends.length; index++) i if (friends [index]- null) £ System.out.println("Friend:" friends [index].name); 192 193 194 friendCount++; 195 196 197 198 199

199 if(friendCount-)t 200 201 System.out.println( There are no friends for "+name); 202 203 204 205 206 207 208 209 210 211 212