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Ch 5 Test

True/False
Indicate whether the statement is true or false.
 

 1. 
Memory for an object’s data is stored as part of the class template.
 

 2. 
Every object has its own unique identity.
 

 3. 
A client needs to know only a server’s interface.
 

 4. 
It is not possible for two variables to refer to the same object.
 

 5. 
A reference variable can be compared to the null value.
 

 6. 
Class names must adhere to the rules for naming variables and methods.
 

 7. 
Instance variables are nearly always declared to be public.
 

 8. 
If a class template contains no constructors, the JVM provides a primitive default constructor.
 

 9. 
You cannot call one constructor from another constructor.
 

 10. 
If the return type of a method is not void, it can be any primitive or reference type.
 

 11. 
Method names have the same syntax as other Java identifiers.
 

 12. 
Helper methods are usually public.
 

 13. 
When an object is instantiated, it gets a complete set of fresh instance variables
 

 14. 
You cannot have a local variable and a global variable with the same name in a class.
 

 15. 
You should use local variables to remember information in an object.
 

Multiple Choice
Identify the choice that best completes the statement or answers the question.
 

 16. 
The combining of data and behavior into a single software package is called ____.
a.
encapsulation
c.
instantiation
b.
invocation
d.
information hiding
 

 17. 
An object has ____ as defined by the methods of its class.
a.
a state
c.
an identity
b.
semantics
d.
behavior
 

 18. 
A server’s data requirements and the implementation of its methods are hidden from the client. This approach is referred to as ____.
a.
garbage collection
c.
encapsulation
b.
information hiding
d.
instantiation
 

 19. 
Messages that change an object’s state are called ____.
a.
modifiers
c.
mutators
b.
accessors
d.
adapters
 

 20. 
Suppose a Student class contains a method setName to set the value of a Student object’s instance variable name, plus a method getName to access the value of name. Consider the following code fragment:

Student s1, s2;
s1 = new Student();
s2 = new Student();
s1.setName(“Bill”);
s2.setName(“Eric”);
s2 = s1;
s2.setName(“Bob”);
System.out.println( s1.getName() );

What would be displayed on the console?
a.
Bob
c.
Bill
b.
Eric
d.
null
 

 21. 
Methods used to initialize a new object are called ____.
a.
initializers
c.
initiators
b.
creators
d.
constructors
 

 22. 
Class definitions usually begin with the keyword ____, indicating that the class is accessible to all potential clients.
a.
accessible
c.
private
b.
public
d.
global
 

 23. 
At the root (base) of Java’s class hierarchy is a class called ____.
a.
Java
c.
Class
b.
Object
d.
Root
 

 24. 
Constructors are activated when the keyword ____ is used.
a.
new
c.
create
b.
construct
d.
object
 

 25. 
Which of the following represents the general form of a method?
a.
<visibility modifier> <return type> <method name> (<parameter list>){

    <implementing code>

}
b.
<return type> <visibility modifier> <method name> (<parameter list>){

    <implementing code>

}
c.
<visibility modifier> <method name> <return type> (<parameter list>){

    <implementing code>

}
d.
<return type> <method name> (<parameter list>){

    <implementing code>

}
 

 26. 
If a method has a return type, its implementing code must have at least one ____ statement that returns a value of that type.
a.
end
c.
break
b.
give
d.
return
 

 27. 
____ variables can be declared in a method to provide temporary working storage for data in the method.
a.
Global
c.
Instance
b.
Local
d.
Internal
 

 28. 
The scope of a ____ is all the methods in the defining class.
a.
global variable
c.
parameter
b.
local variable
d.
constant
 

 29. 
The ____ of a variable is the period during which it can be used.
a.
scope
c.
lifetime
b.
definity
d.
range
 

 30. 
The ____ class includes methods for all but two mouse events, mouse motion and mouse dragging.
a.
MouseAdapter
c.
MouseMotionAdapter
b.
MouseEvent
d.
MouseListener
 

Completion
Complete each statement.
 

 31. 
A(n) ____________________ is a runtime entity that contains data and responds to messages.
 

 

 32. 
A(n) ____________________ is a software package or template that describes the characteristics of similar objects.
 

 

 33. 
An object is an instance of its class, and the process of creating a new object is called ____________________.
 

 

 34. 
Because unreferenced objects cannot be used, Java deletes them during a process called ____________________.
 

 

 35. 
An object has a(n) ____________________, which is another way of saying that at any particular moment its instance variables have particular values.
 

 

 36. 
A client’s interactions with a(n) ____________________ are limited to sending it messages.
 

 

 37. 
Methods that are used to access an object’s state are called ____________________.
 

 

 38. 
At any time, it is possible to break the connection between a variable and the object it references by assigning the value ____________________ to the variable.
 

 

 39. 
When a program attempts to run a method with an object that is null, Java throws a(n) ____________________.
 

 

 40. 
In Java’s class hierarchy, if class A is immediately above another class B, we say that A is the ____________________ of B.
 

 

 41. 
The keywords private and public are ____________________ modifiers.
 

 

 42. 
Constructors with empty parameter lists are called ____________________ constructors.
 

 

 43. 
The visibility modifier ____________________ should be used when you want a method to be available to clients of the defining class.
 

 

 44. 
A method that returns no value should have a return type of ____________________.
 

 

 45. 
Parameters listed in a method’s definition are called ____________________ parameters.
 

 

 46. 
Values passed to a method when it is invoked are called ____________________.
 

 

 47. 
The ____________________ of a variable is that region of the program within which it can validly appear in lines of code.
 

 

 48. 
Variables declared within any compound statement enclosed in braces are said to have ____________________ scope.
 

 

 49. 
The method ____________________ is used to force a refresh of any GUI component, such as a panel.
 

 

 50. 
A program can detect and respond to mouse events by attaching ____________________ objects to a panel.
 

 

Essay
 

 51. 
What does a client need to know in order to use a class?
 

 52. 
Why would some variables be declared as private and others public?
 



 
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