101
THE CompSci UNIVERSITY OF AUCKLAND
SUMMER SEMESTER, 2007
Campus: City
COMPUTER SCIENCE
TEST
Principles of Programming
(Time allowed: 75 MINUTES)
NOTE:
Attempt ALL questions
Write your answers in the space provided
There is space at the back for answers that overflow the allotted space
No calculators are permitted
Surname:
Forenames:
Student ID number:
Login name:
CONTINUED
Question/Answer Sheet
- Page 2 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
CompSci 101 Test Results
Question
Marks
Out of
Question 1
28
Question 2
6
Question 3
10
Question 4
5
Question 5
14
Question 6
6
Question 7
6
TOTAL
75
CONTINUED
Question/Answer Sheet
- Page 3 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
Question 1 (28 marks)
a) What output is produced by the following code?
System.out.println(1 + 2 + "3" + 4 + 5);
3345
(2 marks)
b) What output is produced by the following code?
System.out.println("\"" + "\\nn");
"\nn
(2 marks)
c) Consider the following boolean expression:
(a && b) || (!a)
What values would need to be stored in the boolean variables a and b so that this expression
evaluates to false?
a = true;
b = false;
(2 marks)
CONTINUED
Question/Answer Sheet
- Page 4 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
d) What output is produced by the following code?
int
int
int
int
a
b
c
d
=
=
=
=
1;
2;
3;
Math.max(Math.min(a, b), Math.min(b, c));
System.out.println(d);
2
(2 marks)
e) What output is produced by the following code?
System.out.println((1 + 2 * 3) / 4 + 5);
6
(2 marks)
f)
What output is produced by the following code?
int x = 100;
int y = x;
x = 10;
System.out.print(y);
String s = "10";
String t = s.substring(0,1);
System.out.println(s + t);
100101
(2 marks)
CONTINUED
Question/Answer Sheet
- Page 5 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
g) What output is produced by the following code?
int a = 0;
int b = 7;
a = b;
b = a;
System.out.println(a + b);
14
(2 marks)
h) What output is produced by the following code?
int[] nums = { 1, 2, 3, 4, 5 };
nums[0] = nums[3];
nums[1] = nums[2] + nums[4];
nums[2] = nums.length;
nums[ nums[1] - nums[2] ] = 10;
System.out.print(nums[0]
System.out.print(nums[1]
System.out.print(nums[2]
System.out.print(nums[3]
System.out.print(nums[4]
+
+
+
+
+
"
"
"
"
"
");
");
");
");
");
4 8 5 10 5
(2 marks)
CONTINUED
Question/Answer Sheet
- Page 6 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
i) The printOutput() method is called in the following way:
printOutput(3.5, 'H', "Hello");
Complete the method header for the printOutput() method (i.e. complete the first line of
the method definition).
private void printOutput(double a, char b, String c) {
System.out.println(a + " " + b + " " + c);
}
(2 marks)
j)
The getLetter() method is called in the following way:
char c = getLetter("Test", 3);
Complete the method header for the getLetter() method (i.e. complete the first line of the
method definition).
private char getLetter(String a, int b) {
return a.charAt(b);
}
(2 marks)
k) What is the number of characters in the String returned by the method call:
s.substring(4, 10)
6
(2 marks)
CONTINUED
Question/Answer Sheet
- Page 7 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
l)
Consider the following class stored in a file called MyApplication.java:
public class MyApplication {
public static void main(String[] args) {
MyProgram p = new MyProgram();
p.start();
}
}
Also consider the following class stored in a file called MyProgram.java:
public class MyProgram {
public void start() {
System.out.println("Hello World");
}
}
If MyApplication.java and MyProgram.java are both stored in the current directory,
give the correct DOS commands required to compile and run this program so that the output
"Hello World" is produced:
javac MyProgram.java
javac MyApplication.java
java MyApplication
or
javac *.java
java MyApplication
or
javac MyApplication.java
java MyApplication
(2 marks)
CONTINUED
Question/Answer Sheet
- Page 8 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
m) What output is produced by the following code?
String a = "c";
String b = "compsci";
String c = b.substring(0,1);
System.out.println(a + " " + c + " " + (a == c));
c c false
(2 marks)
n) What output is produced by the following code?
int[] a = {7, 6, 2, 0, 1};
int[] b;
b = a;
b[3] = 100;
System.out.println(a[3]);
100
(2 marks)
CONTINUED
Question/Answer Sheet
- Page 9 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
Question 2 (6 marks)
What is the output of the following program:
public class MyProgram {
public void start() {
int a = 10;
int b = 20;
if (a < b) {
System.out.println("one");
}
if (a == b) {
System.out.println("two");
}
if ((a + b) > 0) {
System.out.println("three");
}
if (a < b) {
System.out.println("four");
} else if (a == b) {
System.out.println("five");
} else if ((a + b) > 0) {
System.out.println("six");
} else {
System.out.println("seven");
}
}
}
one
three
four
(6 marks)
CONTINUED
Question/Answer Sheet
- Page 10 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
Question 3 (10 marks)
Consider the following start() method:
public void start() {
int c1 = (int)(Math.random()*13) + 1;
int c2 = (int)(Math.random()*13) + 1;
if (isBlackjack(c1, c2)) {
System.out.println("A blackjack!");
}
}
The start() method deals two cards, storing their numeric values in the variables c1 and c2. It
then calls the isBlackjack() method to test whether the two cards form a blackjack, and prints
out "A blackjack!" if they do.
To answer this question, you need to define the following TWO methods:
... isBlackjack(...)
... cardValue(int cardNumber)
The cardValue() method is passed the number of a card as a parameter. The number 1
represents an Ace, numbers 11, 12 and 13 represent the Jack, Queen and King picture cards
respectively, and any number between 2 and 10 represents a card with that face value. The
method should then calculate and return the value that the card represents in a game of
blackjack. The value of an Ace is 11, the value of any picture card is 10, and the values of all
other cards are their face values.
The isBlackjack() method is passed the two cards that have been dealt, and must return
true if those cards form a blackjack, and false if they do not (a blackjack is when the sum
of the card values of the two cards equals 21). This method must call the cardValue()
method to obtain the value of each card.
You will need to define appropriate return types for both methods, and appropriate parameters for
the isBlackjack() method.
CONTINUED
Question/Answer Sheet
- Page 11 -
CompSci 101 SS C
SURNAME: ...................................................... ...........................................................
isBlackjack(
){
private FORENAMES: boolean isBlackjack(int c1, int c2) {
int total = cardValue(c1) + cardValue(c2);
return (total == 21);
}
}
(5 marks)
cardValue( int cardNumber ) {
private int cardValue(int cardNumber) {
if (cardNumber == 1)
return 11;
if (cardNumber > 10)
return 10;
return cardNumber;
}
}
(5 marks)
CONTINUED
Question/Answer Sheet
- Page 12 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
Question 4 (5 marks)
The formula for converting a temperature from Fahrenheit to Celsius is given below:
Consider the following program which asks the user to enter a temperature in Fahrenheit, and prints
out the result in Celsius:
public class MyProgram {
public void start() {
System.out.println("Temperature conversion");
System.out.print("Enter temperature (F): ");
int input = Keyboard.readInput();
int input = Integer.parseInt(Keyboard.readInput());
int result = convertFahrenheitToCelsius(input);
System.out.println("Celsius = " + result);
}
private int convertFahrenheitToCelsius(int degF) {
int degC = (int)((5/9)*(degF - 32));
int degC = (int)((5.0/9)*(degF - 32));
return degC;
}
}
(5 marks)
There is exactly one syntax error and one logic error in the above code.
The syntax error will be detected by the compiler, and in response the compiler will generate
the following error message:
"incompatible types"
The logic error will not be detected by the compiler but will cause the output to be incorrect.
Circle the line of code that contains the syntax error, and circle the line of code that contains the
logic error and provide corrections for both of these errors underneath the incorrect lines.
CONTINUED
Question/Answer Sheet
- Page 13 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
Question 5 (14 marks)
The following class defines a playing card.
public class Card {
private int cardNumber;
private String suit;
public Card(int num, String suit) {
cardNumber = num;
this.suit = suit;
}
public void setSuit(String suit) {
this.suit = suit;
}
public String getSuit() {
return suit;
}
public void setCardNumber(int num) {
cardNumber = num;
}
public int getCardNumber() {
return cardNumber;
}
public boolean isAPictureCard() {
if(cardNumber > 10 && cardNumber < 14) {
return true;
}
return false;
}
public String toString() {
String cardDesc = "Playing card: ";
if( cardNumber == 11) {
cardDesc = cardDesc + "J";
} else if( cardNumber == 12) {
cardDesc = cardDesc + "Q";
} else if( cardNumber == 13) {
cardDesc = cardDesc + "K";
} else if( cardNumber == 1) {
cardDesc = cardDesc + "A";
} else {
cardDesc = cardDesc + cardNumber;
}
cardDesc = cardDesc + " of " + suit;
return cardDesc;
}
}
CONTINUED
Question/Answer Sheet
- Page 14 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
a) Two objects of type Card are created as follows:
Card card1 = new Card(12, "Hearts");
Card card2 = new Card(1, "Spades");
Complete the diagram below illustrating the values that are stored in the instance variables for each
of these objects. You should write very clearly on the diagram, as you are required to change the
diagram when you complete part (b) of this question.
"Hearts"
suit
card1
cardNumber
12
4
"Spades"
suit
"Clubs"
card2
cardNumber
1
(6 marks)
CONTINUED
Question/Answer Sheet
- Page 15 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
b) Given the two Card objects created and initialised as in the diagram on the previous page, what
would be the output after the following statements are executed? Note: you MUST also mark any
changes to any instance variables clearly on the diagram on the previous page.
card2.setSuit("Clubs");
card1.setCardNumber(4);
if (card1.isAPictureCard()) {
System.out.println("1. Picture card");
} else {
System.out.println("2. Not a picture card");
}
System.out.println("3. " + card2.getSuit());
System.out.println("4. " + card1.toString());
System.out.println("5. " + card2.toString());
The output would be:
2.
3.
4.
5.
Not a picture card
Clubs
Playing card: 4 of Hearts
Playing card: A of Clubs
(8 marks)
CONTINUED
Question/Answer Sheet
- Page 16 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
Question 6 (6 marks)
What is the output of the following program:
public class MyProgram {
public void start() {
int a = 10;
methodOne(a);
System.out.println(a);
}
private void methodOne(int a) {
a = a + 1;
a = methodTwo(a);
System.out.println(a);
}
private int methodTwo(int x) {
System.out.println(x);
return x + x;
}
}
Show the output here:
11
22
10
(6 marks)
CONTINUED
Question/Answer Sheet
- Page 17 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
Working for Question 6:
Diagrams of the method calls are not required but partial credit may be given for working if the
output is incorrect.
start()
a: 10
methodOne(10)
a: 10 11 22
22
methodTwo(11)
x 11
CONTINUED
Question/Answer Sheet
- Page 18 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
Question 7 (6 marks)
What is the output of the following program:
public class MyProgram {
public void start() {
int[] x = {1, 2, 3, 4, 5, 6};
int[] y = process(x);
for (int i = 0; i < y.length; i++) {
System.out.print(y[i] + " ");
}
}
private int[] process(int[] a) {
int[] result = new int[a.length / 2];
for (int i = 0; i < result.length; i++) {
result[i] = a[i*2] + 1;
}
return result;
}
}
246
(6 marks)
CONTINUED
Question/Answer Sheet
- Page 19 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
OVERFLOW PAGE
(If you have used this page, please indicate clearly under the
relevant question that you have overflowed to this page)
CONTINUED
Question/Answer Sheet
- Page 20 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
ROUGH WORKING (WILL NOT BE MARKED)
(You may detach this page from the answer booklet and use it for rough working)
CONTINUED
Question/Answer Sheet
- Page 21 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
ROUGH WORKING (WILL NOT BE MARKED)
(You may detach this page from the answer booklet and use it for rough working)
Question/Answer Sheet
- Page 22 -
CompSci 101 SS C
SURNAME: ...................................................... FORENAMES: ...........................................................
APPENDIX:
Useful methods and variables:
String
public
public
public
public
public
public
int indexOf(char c)
int indexOf(String string)
char charAt(int index)
String substring(int beginIndex, int endIndex)
int length()
boolean equals(String comparison)
StringTokenizer
public boolean hasMoreTokens()
public String nextToken()
Math
public static double random()