ITEC 120 2007spring ibarland, jpittges

home—info—exams—lectures—labs—hws
Recipe—Laws—lies—syntax—java.lang docs—java.util docs

hw01
hw01
calling functions (from functions)

Due Date: Jan.22 (Mon.), 17:00. ¹

Instructions:

• This homework includes some short-answer questions (1-5), and some programs (6-8). You can either do all of these in one big file (with your short-answer questions being in one big comment at the start or the end of your java program), or in two separate files.
• As always, submit your assignment via Blackboard, and also bring a hardcopy to the following class.

1. (2pts) For each of the following pieces of information, what is the most appropriate Java type to represent them? (The Java types we have covered are int, double, String).
   1. The number of PS-3s in stock, at a certain store.
   2. The current sale price of a PS-3 at that store, in dollars.
   3. The current sale price of a PS-3 at that store, in cents.
   4. The serial number of a particular PS-3 (something like 4QJ7B93).
2. (3pts) Suppose class Blizgrffblop contains a method with whose signature is

   int fizzle( String s )

   If bz is an instance of class Blizgrffblop,
   1. Call fizzle, passing it the string "hmmm".
   2. Call fizzle, passing it the empty string.
   3. Call fizzle, passing it the empty string, and dividing the result by 12.3.
3. (1pt) Write the signature for a method named flarg, which takes in a (possibly-fractional) number, and returns a number (which is always a whole number).
4. (1pt) Write the signature for a method named shlark, which takes in a two pieces of text, and returns a (possibly fractional) number.
5. (3pts) Conventions and comments:
   1. True/False: in the examples in lecture, the name of each class starts with a capital letter.
   2. True/False: in the examples in lecture, the name of each function within a class starts with a capital letter.
   3. A Javadoc comment begins with what special 3-character sequence?                 
   4. What Javadoc “@” keyword indicates that you are describing one of the parameters of the function?
   5. What immediately follows that keyword?

6. (8pts) 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 temperatures² are freezing (0°C, which is 32°F), and boiling (100°C, which is 212°F).

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

   F(C) = ⁹⁄₅ · C + 32

   Write a java function celcToFahr, which takes a temperature in °C, and returns that temperature expressed in °F.

   Careful: Because of how Java does arithmetic, 9/5 evaluates to 1 (recall hw00). Instead, write 9.0/5.0. We'll discuss what's happening in a week or two.

   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.

   
   
7. (8pts)

   You read in a science article that the surface of the sun is 5700K (“kelvins”³), 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.

   Write a function kelvToFahr to convert temperatures in Kelvins to temperatures in °F.
   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?

   Be sure to spend time getting your test cases right; they will help you figure out how to solve the general problem.

   Your function can either have just a single return statement, or it can use a named constant local variable to store an intermediate result (presumably: the temperature in °C), before calculating and returning the final result.

8. (4pts) Write kelvToFahr_v2, which gives exactly the same answers as kelvToFahr, except that it uses a local variable (if your first version didn't), or doesn't use a local variable (if your first version did). Follow the syntax in class for local variables: one line declares the variable, and the very next line initializes it.

home—info—exams—lectures—labs—hws
Recipe—Laws—lies—syntax—java.lang docs—java.util docs

For these last problems, where you write functions, put them inside

class TempConverter {




  }

1. Write Test cases.
   It's convenient to write these test cases in the same style you'd use to call the function:

   h(5) = 23 /* Well, instead of 'h', use your particular function name. */ h(0) = 14 ...

2. Then write the signature for the function (the name of the function, the name&type of any input(s), and the function's return type), followed by…
3. Then write the javadoc comment (including a short one-line description, an @param line, and an @return line.)
4. Finally, write the body of the function (which will include return expression;)
5. You'll want to check your test cases, to make sure your function really works as advertised. (If your function fails any test cases, indicate so in your comments.)
6. Go back and double-check whether your functions meets the Laws of Programming:
   1. No repeated code. (Only one place in your code should mention 9.0, 5.0, and 32.)
   2. Human-readable (good indenting, spacing, meaningful names);

home—info—exams—lectures—labs—hws
Recipe—Laws—lies—syntax—java.lang docs—java.util docs

©2007, Ian Barland, Radford University Last modified 2007.Aug.27 (Mon)

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