What e) is printed by the following?
CompSci 101 S1 2004 City and Tamaki
System.out.println(5 + 9 % 2 * (10 / 4) - 6);
Terms Test Model Answers
1
Question 1 (20 marks)
(2 marks)
a) What is printed by the following?
f) What is printed by the following?
System.out.println("5" + 5 + 9);
System.out.println(5 / 2.0 * 3 / 5);
559
(1 mark)
1.5
(1 mark)
b) What is printed by the following?
g) What is printed by the following?
System.out.println(6 + 3 + "8");
String string01 = "food looks good";
System.out.println(string01.indexOf("oo",4));
98
(1 mark)
6
(2 marks)
c) What is printed by the following?
System.out.println((int) 5.3);
h) What is printed by the following?
System.out.println(Math.pow(Math.max(4,3), 2));
5
(1 mark)
16.0
(2 marks)
d) What is printed by the following?
System.out.println("\"n\\\n\"");
i) What is printed by the following?
"n\
"
System.out.print((int)3.14159 + "\nis the");
System.out.print("value of pi.");
(2 marks)
3
is the value of pi.
(2 marks)
j) What is printed by the following?
Question 2 (10 marks)
String string02 = "abcdefghij";
System.out.println(string02.substring(3,string02.length()-3));
Consider the following section of Java source code, and answer the questions below:
int x = 5;
int y;
char c = a;
defg
y = (int)Math.pow(x,2);
Rectangle aRect = new Rectangle(x,y,30,20);
String rectString = "Rect1" + " is " + aRect.toString();
(2 marks)
k) What is printed by the following?
String string03 = " 11 22 33 ";
String string04 = string03.trim();
string04+=3;
System.out.println(string04);
a)
List all the identifiers which appear in the above code fragment
String, Math, Rectangle,
x, y, c, aRect, rectString
pow, toString
11 22 333
(2 marks)
(5 marks)
l) What is printed by the following?
b)
Identify all the variables in the above code fragment and categorize them according to
whether
they are primitive or object types.
double number01 = 12;
int number02 = 5;
number01 -= number02;
System.out.println(number01);
PRIMITIVE VARIABLES:
x, y, c
7.0
(2 marks)
OBJECT VARIABLES:
aRect, rectString
(5 marks)
Question 3 (10 marks)
Question 4 (15 marks)
You need to find and correct five errors in the program Q3. There is no more than one error on each
line of code.
Complete the application Q4 given below. Your application should perform the following tasks.
The application program Q3 is supposed to generate a random number between 0 and 26, and then
print out that number of letters from the alphabet. Three examples of the application being executed
are shown below the output must be identical to that shown:
1.
2.
3.
4.
Example 1:
C:\>java Q3
The first 5 characters of the alphabet are abcde
Two examples of the output that must be produced by your Q4 program are given below. Make sure
the output of your application is identical to the format of this output. Values entered by the user are
given in bold:
Example 2:
C:\>java Q3
The first 0 characters of the alphabet are
Example 3:
C:\>java Q3
The first 18 characters of the alphabet are abcdefghijklmnopqr
The source code for the application Q3 is given below. Five of the lines of code contain an error of
some sort. For each error, you need to clearly circle the error and provide a correction so that the
program will compile and execute correctly. You do not need to write out the whole line of source
code again, as long as you indicate your corrections clearly.
public class Q3 {
1
Prompt the user to enter two integer values as input.
Print the word "Larger:" followed by the larger of the two input integer values.
Print the word "Difference:" followed by the difference between the larger and smaller
input values.
Print the word "Quotient:" followed by the real value obtained by dividing the first input
value by the second input value.
public static void main(String[] args){
String alphabet = "abcdefghijklmnopqrstuvwxyz";
2
int index;
3
index = (int) ( Math.random() * 27 );
4
System.out.println("The first " + index + " characters of
the alphabet");
5
System.out.println(" are " + alphabet.Ssubstring(0,
index));
}
}
(10 marks)
Example 1:
C:\>java Q4
Please input first number: 5
Please input second number: 8
Larger: 8
Difference: 3
Quotient: 0.625
Example 2:
C:\>java Q4
Please input first number: 10
Please input second number: -3
Larger: 10
Difference: 13
Quotient: -3.333333333333333335
Complete the source code for this application below. Some variables have been declared for you:
Question 5 (15 marks)
import java.io.*;
Complete the implementation of the FruitProfile class for building simple fruit profiles in a
grocery store. The application Q5 makes use of the FruitProfile class as shown below.
public class Q4 {
public class Q5 {
public static void main(String[] args){
public static void main(String[] args) {
int number1;
int number2;
int difference;
double quotient;
FruitProfile fruit1 = new FruitProfile("apple", 10);
FruitProfile fruit2 = new FruitProfile("pear", 16);
System.out.println(fruit1.toString());
fruit1.add(12);
System.out.println("After adding");
System.out.println(fruit1.toString());
System.out.print("Please first input number: ");
number1 = Integer.parseInt(readInput());
System.out.println();
System.out.println(fruit2.toString());
fruit2.subtract(5);
System.out.println("After subtracting");
System.out.println(fruit2.toString());
System.out.print("Please input second number: ");
number2 = Integer.parseInt(readInput());
difference = Math.max(number1,number2)
Math.min(number1,number2);
System.out.println("There are currently " +
fruit1.getAmount() + " " + fruit1.getName() +
"(s) in store." );
quotient = (double)number1/(double)number2;
System.out.println("Larger: " + Math.max(number1,
number2));
System.out.println("Difference:" + difference);
System.out.println("Quotient:" + quotient);
private static String readInput() {
try {
BufferedReader in = new BufferedReader(
new InputStreamReader(System.in));
return in.readLine();
}
catch (IOException e) {}
return "";
}
}
}
The application Q5 shown above uses the FruitProfile class to create two FruitProfile
objects. When a FruitProfile object is constructed, the name of the fruit (a String) and the
amount in store (an int) are both specified. Given a correct implementation of the
FruitProfile class, the output from the application above should be exactly as shown below.
(15 marks)
}
}
C:\>java Q5
Fruit name: apple
Amount: 10
After adding
Fruit name: apple
Amount: 22
Fruit name: pear
Amount: 16
After subtracting
Fruit name: pear
Amount: 11
There are currently 22 apple(s) in store.
Complete the implementation of the FruitProfile class from the skeleton file given below.
Question 6 (10 marks)
public class FruitProfile {
(a) Evaluate the following boolean expressions
// instance variables
private String name;
private int amount;
(i)
true
//constructor
public FruitProfile(String inputName, int inputAmount){
(1 mark)
name = inputName;
amount = inputAmount;
(ii)
}
3==4 && 3 != 4 || !(3 != 3) && !(4 != 4) || 5 <= 4
true
(1 mark)
// add(): adds input amount to current amount
public void add(int inputAmount) {
amount += inputAmount;
}
(iii)
// subtract(): subtracts input amount from current amount
public void subtract(int inputAmount) {
amount -= inputAmount;
}
! ( ! (4 != 6) && !(5 >4))
true
(1 mark)
(b) DeMorgan's Law consists of the following two equivalences:
// getName : returns name of fruit
public String getName() {
return name;
}
!(A && B) == !A || !B
!(A || B) == !A && !B
// getAmount : returns amount of fruit
public int getAmount() {
return amount;
}
Use DeMorgan's Law to help simplify the following expression. The simplified expression should
not contain either of the symbols ! or !=
!(!(x > 42) && !(x <13))
// toString : returns String representation of fruit and
current amount
public String toString() {
return "Fruit name: " + name + "\n" + "Amount: " +
amount;
}
}
(2 > 3) || (4 == 4) && !((4>5) || (2<3)) || (9!=2)
x>42 || x<13
(3 marks)
(15 marks)
(b) What is the output of the following code?
(c) Complete the truth table for the following boolean expression
P && Q || !(P || Q) && P
P
Q
P&&Q
P||Q
!(P||Q)
!(P||Q)&&P
P&&Q || !(P||Q)&&P
T
T
F
F
T
F
T
F
T
F
F
F
T
T
T
F
F
F
F
T
F
F
F
F
T
F
F
F
(4 marks)
Question 7 (10 marks)
int x = 4;
int y = 5;
int z = 6;
if(x>y || y>z)
x = 0;
else
if(x<y && y<z)
if(x==y)
z=y;
else
y = 0;
else
if(y==0 || x<z)
z = 0;
System.out.println(x + " " + y + " " + z);
(a) Translate the following sentences from English to Java
(i) If a is less than 7 or b is greater than 7 then print out "greater than 7"
406
(5 marks)
if( a<7 || b>7)
System.out.println("greater than 7");
Question 8 (5 marks)
(1 mark)
(ii) Print "too easy" unless finalMark is less than 50
Assume that variables r and s have been declared as follows:
Rectangle r = new Rectangle(10,20,30,40);
Rectangle s = new Rectangle(10,20,30,40);
(i) Write an if statement which will print out "equal value" if r is equal in value to s.
if( !(finalMark < 50) )
System.out.println("too easy");
(1 mark)
if ( r.equals(s) )
System.out.println("equal value");
(iii) Print "too hard", but only if finalMark is less than 50
(2 marks)
(ii) Write an if statement which prints out "equal reference" if r is equal in reference to s.
if( finalMark < 50 )
System.out.println("too hard");
(1 mark)
if ( r==s )
System.out.println("equal reference");
(iv) If either a or b is greater than 8 and if neither c nor d is less than 8, then print "abcd"
(2 marks)
(iii) Are the two variables r and s equal in reference, equal in value, or both?
if( (a>8 || b > 8) && !(c<8 || d<8) )
System.out.println("abcd");
equal in value
(2 marks)
(1 mark)
Question 9 (5 marks)
What is the output of the following code?
int x = 25;
int y = 10;
int count = x;
System.out.println("Before: " + count);
while(count > y){
if(count%5==0)
System.out.println(count);
count--;
}
System.out.println("After: " + count);
Before: 25
25
20
15
After: 10
(5 marks)