CS535: Past Exams

	CS 535: Object-Oriented Programming & Design

Fall Semester, 1997
Past Exams
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San Diego State University -- This page last updated 16-Oct-97

Contents of Past Exams

Here are the exams given in this course in previous years. Please note that this course does change from year to year. As a result the exams change each year.

1) a) We have a class A which has a protected field P. Explain where the protected field P is accessible and where it is not accessible.

b) We have a class A which has a field N, with no explicit access level given. Explain where the field N is accessible and where it is not accessible.

2) a) What is a NaN?
b) Under what conditions will a NaN be generated in Java?

3) What is a constructor? When are they called?
b) What is the role of a finalize method? When is it called?

4) What are the differences between an abstract class and an interface in Java?

5) a) What makes an exception check or unchecked?
b) How can a Java program treat an unchecked exception differently than a checked exception?

6) Let a child and parent class both have a method, public void foo(), with the same signature. The rules for determining which foo() is executed at run time can be summarized as: "overridden methods are resolved dynamically". Explain why hidden fields can not be resolved dynamically.

7) What is super? Give an example of when you would use "super".

8) We have two classes A and B. What relationship between A and B do the following phrases indicate. Please indicate the role of A and B in the relationship. For example: A is the parent of B.

a) Is-kind-of
b) is-analogous-to
c) has-a

9) True or False. A Java class A has a final field F. All objects created from class A must have the same value for F.

True or False. An access of a non static method is always resolved dynamically.

True or False. The average number of fields per class should be less than 6.

True or False. If a child class constructor does not explicitly call it's parent's constructor, then the parents constructor is not called when creating a child object.

10) What is the result of compiling and if they compile executing the following programs?
a)

class  Test
   {
   public static void A()
      {
      int  array[] = new int[5];
      try  
         {
         System.out.println( "Start Try"  );
         array[  10  ]  =  1;
         }
      catch (  Exception error  )
         {
         System.out.println( "Exception " );
         throw error;
         }
      finally
         {
         System.out.println(  "Final Block"  );
         return;
         }
      }
      
   public  static  void  main( String  args[]  )
      {
      try {  A();  }
      catch  (ArrayIndexOutOfBoundsException error ) 
         {
         System.out.println(  "In Catch"  );
         }
      System.out.println(  "After try in main"  );
      }
   }

b) 
class  Test
   {
   String message = "Global";

   public static void A( String message)
      {
      message = message + "End";
      }
      
   public  static  void  main( String  args[]  )
      {
      String message = "Main";
      A( message );
      System.out.println( message );
      }
   }

class Parent
   {
   public Parent()   
      { 
      System.out.println( "Parent" ); 
      }

   public Parent( double value )   
      { 
      System.out.println( "Parent value "  + value );  
      }
   }

class  Child extends Parent
   {
   public Child( String message )
      {
      System.out.println( "Child " + message );
      }
   
   public Child( double value )
      {
      System.out.println( "Child value " + value );
      }

   public  static  void  main( String  args[]  )
      {
      Child A = new Child( 5.5 );
      Parent B = new Child();
      }
   }

Fall 1995

MidtermExam

1) List the different ways to implement implicit type conversion in a class.


2) If a class has a pointer as a data member, what items should be part of the class to prevent various pointer problems.


3) a) True or False. A copy constructor does not have initialization phase.


b) Give two different types of items that must be initialized in the initialization phase of a constructor.

4) Explain the object-oriented meaning of the following terms.
a) client-server

b) responsibilities

c) scenario


5) a) How do the variables A and B differ?

char  *const  A  =  "Hi"; 
const  char*  B  =  "Hi";

b) Explain the problems with the following uses of C and D

const  char*  C  =  "hi mom";   
C[3] = 'a';

char  *const  D  =  "hi mom"; 
D = "hi dad";


6) We have two entities A and B. What relationship between A and B do the following phrases indicate. Please indicate the role of A and B in the relationship. For example: A is the parent of B.

a) A is a B

b) A is part of B

c) A uses B

d) A is kind of B


What is the output of the following programs?

7)

#include <iostream.h>

void functionA( int X, double Y) { cout << "First function\n";};

void functionA( char X, float Y ) { cout << "Second function\n";};

main() {
   char Me = 'a';
   int You = 5;
   functionA( Me, You );
}

8)

#include <iostream.h>

class Container {
   public:
      int value;

      Container( int amount ) { value = amount;  
                  cout << "Value " << value << endl; };

      ~Container() { cout << " You just killed: " << value << endl; };
};

class ExamQuestion {
   public :      
      Container data;

      ExamQuestion(int A) : data(A) { cout << "New Object\n";};

      ExamQuestion( const ExamQuestion& X ) : data(X.data.value + 10)
                     { cout << "Special\n"; };
};

void TrickyPart(ExamQuestion why)
{
   ExamQuestion PartB = why;   

   cout << "After PartB\n";
}
   
void main()
{   
   ExamQuestion Answer(1);   
   cout << "Call TrickyPart\n";

   TrickyPart(Answer);      
   cout << "end" << endl;
}

What is the result of compiling and running (if they compile) the following programs.

class Test {
   private :
      float data;

   public :
      void setData( int& value) { data = value;};

      static float getData()   { return data;};

      Test( int value ) : data( value ) {};
};

#include <iostream.h>

void main()
{
   Test me = 10.5;
   cout << me.getData() << endl;
}

10) 
int A = 10;

float functionB( int A, char B = 5, float C ) {
   return ::A + B + C;
}

#include <iostream.h>

main() {
   int A = 2;
   float X = 11.1;
   cout << functionB( A, X );
}

Final Exam

1) A data member can be declared public, private, or protected. A base class can be inherited via public, private, or protected inheritance. Explain the effects of private and protected inheritance on the access derived class has of the public and protected data members of the bass class.

2) A base class has a data member called "Foo". The derived class also implements a data member of the same name "Foo". Explain how a function member of the derived class can access the base's data member "Foo".

3) What problem does multiple inheritance cause? How does C++ solve the problem?

4) What are the major steps in the Wirfs-Brock design process?

5) What is the difference between a superclass and a subsystem?

6) a) What is an abstract class?

b) How do you indicate an abstract class in C++?

7) Given classes A and B, what is the most likely relationship between A and B indicated by the phrases:

a) A is a kind of B

b) A uses B

c) A is similar to B

d) A depends on B

e) A has knowledge of B

8) What is the output of the following program?

#include <iostream.h>
class ClassA {
   public:
      virtual void Print() {   cout << "Class A\n"; }
};

class ClassZ :  public ClassA  {   
   public:
      void Print() {   cout << "Class Z\n";}
};

main()
{
   ClassZ* Zpointer = new ClassZ;
   ClassA* Apointer  = new ClassA;
   ClassA   Avariable;
   
   Zpointer->Print();
   Apointer->Print();

   Apointer = Zpointer;
   Avariable = *Zpointer;

   Apointer->Print();
   Avariable.Print();
}

9) What is the output of the following program?

#include <iostream.h>
class A  { 

   public : 
      A(int a = 0)    {cout << a << "A\n" ;}
};

class B :  public A    { 

   public : 

      B(int b = 0) : A(b - 1)   {cout << b <<"B\n" ;}
}; 

class C :  public A { 

   public :  
      B DataMember; 

      C(int c = 0) : A(c-1)    {cout << c << "C\n" ;}  
};


class Test :   public C, public B, public A  {

   public: 
      C State;
      Test() : State(10),  C(50),  B(40),  A(30) { cout << "Test\n"; }; 
};


main () {
   Test me;
   cout << "Done" << endl;
};

Fall 1994

MidtermExam

1. What is the difference between private and protected class members.

2. What is "this". Give an example of when you would use "this".

3. What are the initialization and the assignment phases of a constructor? What is each used for?

4. Having a pointer as a class data member can lead to some undesirable side effects. What should you add to a class to avoid these side effects?

Each of the following programs illustrates one or more concepts or issues in C++. What is/are those issues? What is the result of compiling and running each program? (Some programs may not compile.) Explain your answer. Assume iostream.h is included in each program. Any minor syntax errors are typos.

5a)

void you( long,  long ) {cout << "long"};
void you( double, double ) {cout << "double"};

main()
{
   int got, me;
   dont( got, me );

}

5b)

main()
{
const  char*  what  =  "Is This";   
pc = "Interesting"               cout << *what;
what[3] = 'a';               cout << *what
}

6a)

int& Now()  {
   int Where = 1;
   return Where ;
}

main() {
   int Where;
   Where= Now();
   cout << Where;      
}

6b)

class Where {
   public:
      int here;
   
      int me() const;
      int you() const;
};

int Where ::me() const {
   this->here = here + 5;               return this->here;
}

int Where ::you() const {
   return here + 5;
}

int OhNo(const Where* Now)
{
   return Where->you();
}


main()
{
   Where* IsIt = new Where;
   cout << OhNo(IsIt);
};

7a)

class Top
{   public:
      int a;
      Top(int x) { a = x;}

};

class Bottom : public Top
{   public:
      int b;
      Bottom() { b = 0; a = 0;}   };


void main()
{   
   Bottom barrel;
   cout << barrel.a << barrel.b;         
}

7b)

class Top
{
   public:
      Hat(char *string) {   cout << "Top";}
      Hat(float a) {   cout << "Top Too";}
};

class Bottom :  public Top
{   
   public:
      Hat(const int a) {   cout << "Bottom";}
      Hat(float a) {   cout << "Bottom Too";}
};

main()
{
   Bottom* Rung;
   Rung->Hat(5.5);
   Rung->Hat("cat");

}

class Trouble
{   public:
   Trouble() { cout << "Start Trouble";}
   ~Trouble() { cout << "End Trouble";}
};

class Big : public Trouble
{   public:
   Big() { cout << "Start Big";}
   ~Big() { cout << "End Big";}
};

class Dont
{   public:
   Big deal;
   Dont() { cout << "Start Dont";}
};

main()
{
   Dont DoThisToMe;
}

Final Exam

1. Give the output of the following program.
#include <iostream.h>

class Top {
public:
   virtual void MyMemory() { cout << "I forget" << endl;};
   void Disk()    { cout << "Space" << endl;};
   void Erased()    { cout << "For good" << endl;};
   void ThisExam()    { Erased(); MyMemory(); };
};

class IsOver : public Top {
public:
   void MyMemory()    { cout << "Gone" << endl;};
   void Disk()       { cout << "Slipped" << endl;};
   void virtual Erased()    { cout << "Rubbed out" << endl;};
};
void main()
{
   Top* Hat = new IsOver;
   Hat->MyMemory();
   Hat->Disk();
   Hat->ThisExam();

   Top Dog = *(new IsOver);
   Dog.MyMemory();
   Dog.Disk();
   Dog.ThisExam();
}

Mini-Adventure (MA). The game MA consists of a maze of rooms. A room consists of four walls and one or more doors. Doors can be either open, close, or closed and locked. Some locked doors are opened by a key, others are opened by a magic phrase. Each key opens only one door, except for the master key. Doors lead into other rooms. Rooms are rectangular shaped. Long skinny rooms are called hallways. Rooms may contain gold coins, keys, and/or scrolls with magic phrases. When picked up, scrolls self destruct in a fixed amount of time. This time differs for each scroll. The goal of the game is to explore the rooms and collect as much gold as possible. A player can move around using commands as: goUp, goDown, goLeft, goRight, gotoX where X can be Door, key, scroll, and pickUpX where X can be key, scroll, and gold. Each time a game is played a new maze is created and the player starts in a randomly selected room. A player can see on the screen only the contents of the current room and the outline of rooms they have already been in.

2 a. Give a list of potential classes for the MA game.

b. Pick a class from part a. and give a list of responsibilities for the class,

3. Give a detailed scenario for the game MA involving the class in problem 2b.

4. a. What is an abstract class?
b. What is the purpose of abstract classes in object-oriented programming?

5. Define the following terms in object-oriented programming.
a. client-server

b. contracts

c. protocol

6. What is permitted and what is not permitted by the law of Demeter?

7. a. Why do some object-oriented experts recommend programmers avoid case (and if) statements?

b. Give two alternative mechanisms to case (and if) statements.

Fall 1993

Final Exam

1) Explain the object-oriented meaning of the following terms.

a) abstraction

b) encapsulation

c) information hiding

2) What problem(s) does multiple inheritance have that single inheritance does not?

3) a) What is polymorphism?

b) Give an example of polymorphism in C++.

4) Why is polymorphism important in object-oriented programing?

5) We have two classes A and B. What do the following relationships indicate about the two classes:

a) A is-a B

b) A has-a B

c) A is-kind-of B

d) A is-analogous-to B

e) A depends-upon B

6) a) What is a scenario?

b) What role(s) do scenarios play in object-oriented design.

7) Identify the classes in the following description of a refrigerator. List at least one responsibility for each class.

A refrigerator has a motor, a temperature sensor, a light and a door. The motor turns on and off primarily as prescribed by the temperature sensor. However, the motor stops when the door is opened. The motor restarts when the door is closed if the temperature is too high. The light is turned on when the door opens and is turned off when the door is closed.

8) a) What is a subsystem?

b) What is the purpose of a subsystem in the Wirfs-Brock object-oriented design process?

c) Why are subsystems found toward the end of the process, rather than at the beginning?

9) What is a contract? Give an example.

10) Briefly describe the steps in the Wirfs-Brock object-oriented design process.

11) What is a virtual function in C++? How does a virtual function operate?
How is inheriting a virtual function different than inheriting a normal functions members?

visitors since 16-Oct-97

Contents of Past Exams

Fall 1996

Midterm Exam

Fall 1995

MidtermExam

Final Exam

Fall 1994

MidtermExam

Final Exam

Fall 1993

Final Exam