C Sc 335 Fall 2006 Answers to Practice Test 1
The answer could have been any of these first three bullets
1. Object:
•A module that makes up part of a system
•A software model of a real world entity (account), concept (strategy), or part of a utility (network data
base, GUI, event)
•A bunch of bits in the memory of the computer
Extra explanation fo 1 follows
Every object has
1) an identity a reference variable to find the object
2) methods a.k.a. functions
3) variables: the values that the object remembers
2. Class:
•A blueprint for objects of that type
•An OO way to implement a type as a set of operations and data
•Code that descrobe the method and variables
Relationship between a class diagram and two instance diagrams (on the right) after these two
constructions
BankAccount anAcct = new BankAccount("Stoers", 333.33);
BankAccount acct2= new BankAccount("Daly", 75.00);
3. Keeps related data and methods together
4. The method or variable can be accessed anywhere an object of that type can be declared (unloess
shadowed)
5. Polymorphism in action
•toString
•addActionListener
1
-String my_ID
-double my_balance
+withdraw(double amount)
+deposit(double amount)
+double getBalance( )
+String getID( )
+String toString()
BankAccount
BankAccount: anAcct
my_ID = "Stoers"
my_balance = 333.33
my_ID = "Daly"
my_balance = 75.00
BankAccount: acct2
class name
instance
variables
methods
instance
(object)
instance
(object)
state
state
