ITEC 120 2010fall ibarland

home—info—lects—labs—exams—hws
tutor/PIs—java.lang docs—java.util docs

hw01
Temperatures on the Moon
a first function

due Sep.13 (Mon)

Instructions: Type into a BlueJ file, and submit both a hardcopy in class, plus electronically via Blackboard: Blackboard > Assignments > hw01 > Add attachment; attach TempConverter.java, which is inside the project folder (which in turn should be inside your itec120 folder inside your H drive).

Windows users: Windows Explorer hides the “.java” suffix, so if you see a file TempConverter with no suffix, that's really the .java file. Do not submit files with other suffixes (no “.class” or “.ctxt” files).

In some odd countries (namely Canada, and most of the rest of the world), temperatures are measured in degrees Celcius, instead of degrees Fahrenheit. So when you are traveling and you look in the newspaper and see a forecast for 22°C, it might sound chilly until a friendly Canadian citizen tells you that this is a balmy 71.6°F.

Some other notable temperatures¹ are freezing (0°C, which is 32°F), and boiling (100°C, which is 212°F). (However: if you want to internalize metric, you're better off thinking in terms of new reference points than converting.)

The general case for converting degrees-Celcius into degrees-Fahrenheit is given by the arithmetic formula

F(C) = ⁹⁄₅ · C + 32

From Futurama The Series Has Landed:

Fry: Ooh, nighttime on the moon!
Old coot: It git down to minus one hundr'd, sev'nty-three.
Fry, worriedly: Fahrenheit, or Celsius?
Old coot: First one, then th' other.

1. (0 pts) Make a new BlueJ project (named something like hw01, in the itec120 folder you made on your H-drive). Within the project, make a new class named TempConverter, delete all BlueJ's provided text, and paste in the following:

   /** Itec120 hw01. * See http://www.radford.edu/itec120/2010fall-ibarland/Homeworks/hw01.html * @author your name here */ class TempConverter { }

2. (4pts) Write the signature for celcToFahr (and a stub body, so that you can compile the file.).
3. (3pts) Create a test-driver function, which calls celcToFahr on 22, 37 and at least two other values. Be sure to compute and print the expected value as well. (Choose values which are easy to come up with answers w/o needing a calculator.)


You read in a science article that the surface of the sun is 5700K (“kelvins”²), and that absolute zero is (conveniently) 0 Kelvin. These numbers seem even more baffling, until that same cheerful Canadian tells you that to convert a temperature from Kelvins to °C, you simply subtract 273.15.
So 0 K (absolute zero) is -273.15°C, which in turn is -459.67°F, brr.
Similarly, 273.15K (freezing) is 0°C which (as we've seen earlier) is 32°F.

4. (4pts) Write the signature (and a stub body) for kelvToFahr.

5. (3pts) Add calls to your test-driver, checking that kelvToFahr correctly converts 5700 K to (approx) 9800°F, as well as testing three other values. Be sure to compute and print the correct, expected answer as well as what your function actually returns. (Choose values which are easy to come up with answers w/o needing a calculator.)

   This function must be inside the curly-brackets for class TempConverter, but it can be either before or after celcToFahr.

(Update: an earlier version had a cut-and-paste error asking for an additional submission here; you'll actually only submit once after completing the following steps.)

6. (3pts) Now, go ahead and complete the body of the function celcToFahr. That is, translate the arithmetic formula above into Java, just like we did for ufoHeightAt, pizzaArea, or bookstoreAd. For this function, we'll require that the body must be one single return statement, without any helper variables.

   Run the test cases you figured out in part (b).

   Careful: Because of how Java does arithmetic, 9/5 evaluates to 1. Instead, write 9.0/5.0. We'll discuss what's happening soon.

7. (3pts)

   Finally, go ahead and complete the function kelvToFahr. For this function, we'll require that your solution must declare a helper variable and initialize it to something which not the final answer, but contributes to the final answer.

   Hint: If somebody gives you a temperature in Kelvins, converting that temperature into degrees Celsius is pretty easy. How can you then leverage code from the preceding problem, to convert that many degrees Celsius amount into degrees Fahrenheit?

   (Run your test driver, to make sure it works.)

home—info—lects—labs—exams—hws
tutor/PIs—java.lang docs—java.util docs

©2010, Ian Barland, Radford University Last modified 2010.Sep.17 (Fri)

Please mail any suggestions (incl. typos, broken links) to iba�rlandrad�ford.edu