Unit 1 Assignment

Java Basics
AP Computer Science 2021-22 / Dr. Kessner

Reading

You will not be quizzed on the readings. The Unit 1 quiz next week (and every quiz from now on) will be based on the code exercises in the assignment.

On a first reading, you do not need to remember all the details. You just need to know how to look up the details when you need them. As we progress, I will assume that you have read the assigned chapters, so you may need to go back to these readings to refresh your memory. As you write more code, you will start to internalize the details and you won’t have to look up so many things.

• Eck Section 2.1 http://math.hws.edu/javanotes/c2/s1.html

• Eck Section 2.2 http://math.hws.edu/javanotes/c2/s2.html

• Supplemental: Wikibooks Java Programming https://en.wikibooks.org/wiki/Java_Programming

• Optional background reading: Eck Chapter 1 http://math.hws.edu/javanotes/c1/index.html

Code

Use the demo code to do these exercises. The Unit 1 quiz will consist of similar exercises that you will write out by hand. On the quiz you will need to write the body of a given main function (i.e. the code between the braces {}). At this point, you do not need to be able to write the declaration of the class (public class Blah) or the declaration of the main function (public static void main(String[] args)), but you will in the future.

Important: Don’t let yourself get stuck! If you get frustrated, step away from the keyboard. Then try again when you’re fresh, or ask a classmate for help, or ask me. I’m here to help you!

If you struggle on an exercise, do it again the next day, and again until you can do the exercise without hesitation. Have you allocated time in your schedule to write some code every day?

1. Multiples of 3

Write a program that prints the first 10 multiples of 3. You should write a class MultiplesOf3 in a file MultiplesOf3.java

2. FizzBuzz

Write a FizzBuzz program. Your class should be named FizzBuzz and your source file should be named FizzBuzz.java.

Your program should iterate through the first 30 positive integers, printing each one. However, if the integer $n$ is a multiple of 3, print Fizz instead of the number. And if $n$ is a multiple of 5, print Buzz instead. And if $n$ is a multiple of both 3 and 5, print FizzBuzz instead.

Sample output:

1
2
Fizz
4
Buzz
Fizz
7
8
Fizz
Buzz
11
Fizz
13
14
FizzBuzz
16
.
.
.

3. Geometric sequence

Write a program Geometric.java that prints out the first terms of a geometric sequence, i.e. a sequence with a common ratio, for example: 3, 6, 12, 24, 48, …

4. Cubes

Write a program Cubes.java that prints out the cubes of the counting numbers: 0, 1, 8, 27, 64, 125, …

5. Fibonacci sequence

Write a program Fibonacci.java that prints out the first 30 terms of the Fibonacci sequence: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, …

Hint: I find it easiest to think about this problem using 3 variables: $a$ and $b$ slide up the sequence, and we use a temporary variable $c$ to help do this.

Challenge: After you’ve done this exercise, try doing it using only 2 variables.

Challenge: Try printing out the ratios of successive terms of the Fibonacci sequence. The sequence of ratios approaches a limit - do you recognize what this limit is?