Using if statements to clean up output
COSC 135 A, February 19
Tom Linton, Central College In this activity, you will use if statements to improve code that calculates the number of dollars, quarters, dimes, nickels, and pennies needed to make change for a monetary amount provided by the user. Briefly, you will eliminate output similar to "0 dimes" and change output from things like "1 nickels" to the more appropriate "1 nickel".

1. The source code for a Java application that correctly calculates the number of dollars, quarters, dimes, nickels, and pennies for a given number of cents, is located in the folder G:\Lintont\spring03\prog1\chapter6 (this contains an entire BlueJ project that uses the javabook package). Grab a copy of that folder and copy it to your H:\ drive. Open the project in BlueJ and edit the header comments to include your name(s). You can also access just the source code file (on-line version only) by clicking here.
2. Look over the source code, to understand the logic of its design. Using BlueJ, run the program and enter 200, 80, and 30 as inputs to see the need for improving the output when certain values are either zero, or one.
3. Use an if statement to fix things so that whenever numDollars ends up being zero, the output doesn't mention dollars. For now, fix only the part of the program related to numDollars being 0. For example, if you run your updated code on the input 80, you should get:
       You have 80 cents, which is equivalent to
       3 quarters, 0 dimes, 1 nickels, and 0 pennies.
4. Now, modify your code so that if numDollars ends up being equal to 1, the output contains "1 dollar" rather than "1 dollars" (and it still handles zero dollars correctly). Test this code on a few inputs from 50 to 299 (you select which ones, but be sure to try values below 100, between 100 and 200, and over 200) to ensure your code correctly handles inputs that result in zero, one, or two dollars. Again, only worry about the dollars, not the quarters etc. at this point. Try to use nested ifs for this part (so your code should now contain "else if", rather than several non-overlapping ifs). For example, if numDollars >= 2 is determined first, you don't waste time re-checking whether or not numDollars == 1, or numDollars == 0. (unless the test numDollars >= 2 failed). Similarly, if you first determine that numDollars == 0 is true, you don't re-check whether or not numDollars == 1.
5. Once you have dollars behaving properly, you should be able to mimic the dollars code (copy, paste, and edit will be useful here) to ensure that both dollars and quarters produce nice output. Update the output code for quarters, so that you get nice output (in terms of just dollars and quarters) for inputs like 16, 115, 222, 56, and 106.
6. Clean up the code so that it properly handles dollars, quarters, dimes, nickels, and pennies. Whenever the input is positive, you should not have any zeros in your output, and every "1" should be followed by dollar, quarter, dime, nickel, or penny (instaed of dollars, quarters, dimes, nickels, or pennies respectively).
7. Finally, modify your code so that an input of k, which is 0 or a negative value, outputs: You have k cents, which requires no coins.
8. Be sure the names of all persons with who you worked appears in the header comment, and use the digital drop box on blackboard to hand in your final source code file (MakeChange.java).