Description
Warm-up Question 1 (0 points)
Create a file called HelloWorld.java, and in this file, declare a class called HelloWorld. This class
should define only one method called main(). In the body of this method, use System.out.println()
to display “Hello world!”. You can find such a class in the lecture slides; make sure you can compile
and run it properly.
Warm-up Question 2 (0 points)
Create a file called A.java, and in this file, declare a class called A. This class should define only one
method called main(). In the body of this method, use System.out.println() to display the following
pattern:
A
A A
AAAAA
A A
A A
Warm-up Question 3 (0 points)
Practice with Binary:
Humans usually operate in base 10, probably because most of us have ten fingers. When operating in
base 10, we think of numbers as having a ones column, a tens column, a 100s column, etc. These are
all the powers of 10.
There is nothing special about 10 though. This can in fact be done with any number. In base 2, we
have each column representing (from right to left) 1,2,4,8,16,etc. In base 3, it would be 1,3,9,27, etc.
Answer the following short questions about number representation and counting.
1. In base 10, what is the largest digit that you can put in each column? What about base 2? Base
3? Base n?
2. Represent the number seven in base 7.
3. Represent the number seven in base 2.
4. What binary number is equal to the sum of these two binary numbers? 11001101 + 100101010
5. What is the number from the previous part in base 10?
6. What is the binary number for 11010010 – 11000101?
7. And what is the number from the previous part in base 10?
Warm-up Question 4 (0 points)
This question is designed to help you practice with types.
Background: As discussed in the lectures, there are different types of values in programming languages
such as Java. For instance, we can have integers like the number 5, real numbers like the number 5.1,
boolean values like true and false, characters like ‘m’, or more complex types like Strings e.g. “we all
live in a yellow submarine”. We can compare, contrast, display and apply operators to values of these
different types.
Recall also that we can assign values to variables that are declared with the appropriate type: char
for storing characters, int for integers, double for real numbers, boolean for logical values, and several
others.
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When you declare a variable in Java, you need to specify the type. This involves thinking about a real
world piece of data and figuring out what type you should use.
For each of the following, what type would best represent the data? Are there any that cannot be
represented in Java?
1. The name of a day in the week.
2. Your letter grade in the course.
3. Your numeric grade in the course (as a percentage).
4. The name of the planet that your COMP 202 teacher is from.
5. The temperature outside.
6. The mathematical number π
7. The name of the author who wrote the Hitchhiker’s Guide to the Galaxy?
8. The average number of brain cells in a human.
9. The average number of brain cells of a McGill student after three years of parties.
10. The (estimated) number of molecules in the universe.
11. The result of multiplying two integers together
12. The result of dividing an integer by another integer.
13. “Is the date today Sept 11?”
14. Does this string “i am happy” start with the character ’i’?
Warm-up Question 5 (0 points)
Logic
1. What does the following logical expression evaluate to?
(False or False) and (True and (not False))
2. Let a and b be boolean variables. Is it possible to set values for a and b to have the following
expression evaluate as False?
a or (((not b) or (not b)) or (b or (not a)))
Warm-up Question 6 (0 points)
Write a method swap which takes as input two int values x and y. Your method should do 3 things:
1. Print the value of x and y
2. Swap the values of the variables x and y, so that whatever was in x is now in y and whatever was
in y is now in x
3. Print the value of x and y again.
For example, if your method is called as follows: swap(3,4) the effect of calling your method should be
the following printing
inside swap: x is:3 y is:4
inside swap: x is:4 y is:3
Now, create 2 int (integer) variables in the main method. Call them x and y. Assign values to them and
call the swap method you wrote in the previous part.
After calling the swap() method—inside the main method— print the values of x and y. Are they
different than before? Why or why not?
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Part 2
The questions in this part of the assignment will be graded.
Question 1: My first (graded) Java program (50 points)
The following should go inside a class called ParseDigits and thus a file called ParseDigits.java
Write a Java program that takes as input a 5 digit integer number and outputs three different values,
one on each line:
1. The product of the digits
2. The sum of the digits
3. A statement saying which of those two numbers is larger.
The program should obtain its input from String[] args in the main method. That means that the
input will initially be of type String. The input will be in the first position in a list of Strings. You can
access this String-type list element and convert it to an integer using the following statement:
int number = Integer.parseInt(args[0]);
For example, if the number entered is 54321, the program should display:
The sum of the digits is 15
The product of the digits is 120
The product is larger than the sum
You can assume that the input is valid. That is, you can assume that the number entered has five digits,
and that it is a valid non-negative integer number. Be sure to include descriptive text on each line,
explaining what the following number corresponds to.
Question 2: Using Methods for Marking (50 points)
The goal of this question is to have you write several methods that are all very similar in nature in order
to experiment with the different sorts of methods. You should put all of your code into a class Marking
and thus a file Marking.java.
You cannot use any methods from the Math library in solving these problems.
2a)Void method that prints something
Write a method printMaximum that takes as input two double arguments and prints which is the larger
number. You should include both numbers as part of the message. For example, your message could be
“34.0 is larger than -12.2” or “5.0 and 5.0 are the same number”. Note that for full marks, this message
must be written on one line. (Remember that one way to do this is the + operator. Another way is to
recall the difference between System.out.print() and System.out.println()).
Hint: To test your method, you can write a main method like you did in question one.
The main method will not be graded, but without it, you won’t know whether or not your
method works! Your main method should call this method and verify the results. For
example, your main method could be as follows. You should think of other cases to test!
public class Marking {
public static void main(String[] args) {
printMaximum(55,10);
printMaximum(-44, -16);
}
public static void printMaximum(double num1, double num2) {
// your method definition here
}
}
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2b)Method that returns something
The previous method that you wrote is not very general. Remember that one of the key ideas of methods
is to write a general piece of code that can be re-used.
What stops it from being general? Well, your method is only useful if you want to print which number
is larger. Suppose you wanted to use the larger of two numbers to perform some calculation. You don’t
have access to the result of this computation in any other method.
We will now make another method inside the same Marking class that is more general.
Write a method maximum inside of Marking that, like the previous method, takes as input two double
values, but now returns the larger of the two numbers. Your method must not print anything.
To test your method, you will need to call it from your main method. Think about how you can call the
method and get it to display the answer.
2c)A method calling another method
Now that you have a more general maximum method, you will use it as part of a more complicated
operation.
Write a method finalGrade that takes as input four int values and returns the final grade of a comp-202
student. The first value corresponds to the total assignment grade. The second value is the quiz grade.
The third is the midterm and the fourth is the final exam. Recall that if the student does better on the
final than on the midterm, the mark for the final replaces the mark for the midterm. Be sure to use
your maximum method when you do this. For the purposes of this question, all fractional marks must be
rounded down.
For example, a student might have 28 out of 35 for assignments, 4 out of 5 for quizzes, 18 on 20 for
the midterm, and 30 on 40 for the final. The finalGrade method takes these numbers 28, 4, 18, 30
as input, in order, and would output a final grade of 80. A student who instead had marks of 28, 4,
16, 38 would have a final grade of 89 (the midterm grade is dropped in this case, because the student’s
performance in the course is higher using the alternate grading scheme). Be careful with your types
here! This method uses ints, whereas all the other methods used doubles.
What To Submit
You have to submit one zip file with all your files in it to MyCourses under Assignment 1. If you do not
know how to zip files, please ask any search engine or friends. Google might be your best friend with this,
and a lot of different little problems as well.
These files should all be inside your zip.
ParseDigits.java
Marking.java
Confession.txt (optional) In this file, you can tell the TA about any issues you ran into doing
this assignment. If you point out an error that you know occurs in your problem, it may lead
the TA to give you more partial credit. On the other hand, it also may lead the TA to notice
something that otherwise he or she would not.
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