Difference between revisions of "Cycling Speed"
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<pre> | <pre> | ||
− | mdev = circumference[m] * (number front teeth / number rear teeth) | + | mdev = circumference[m] * (number front teeth / number rear teeth) |
</pre> | </pre> | ||
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==Identify and declare all variables and constants== | ==Identify and declare all variables and constants== | ||
− | + | Based on The Boss's email to you, and the description of the program and formula, we can easily identify all the variables and constants important to the solution. <br /> <b>NOTE:</b> some of these variables are dependent on the others. | |
+ | |||
+ | <br /><br/> | ||
+ | CONSTANTS: | ||
+ | <ul> | ||
+ | <li>The number of front wheel teeth - assumed to be 45 everytime</li> | ||
+ | <li>The diameter of the wheel - assumed to be 70cm everytime</li> | ||
+ | </ul> | ||
+ | |||
+ | <p> | ||
+ | Declaration of Constants | ||
+ | |||
+ | <br /><br /> | ||
+ | When declaring constants, we use the keyword <b>final</b>. This ensures that whether it is an int, double, string or any other data type, if it is a <b>final int</b> for example, it cannot be changed throughout the code. | ||
+ | |||
+ | <br/><br /> | ||
+ | As the number of front wheel teeth is a number, we will declare it using "final int" | ||
+ | |||
+ | <pre> | ||
+ | final int FRONT_TEETH = 45; | ||
+ | </pre> | ||
+ | |||
+ | We also know the constant for the diameter is 70cm every-time. However, the diameter is not used in the calculations. Rather, the circumference is used to calculate the meters of development. | ||
+ | |||
+ | <br /><br />So what should we do??? | ||
+ | |||
+ | <br /><br /> | ||
+ | It's simple! Going back to your high school days you know that the <b>Circumference of a circle (wheel) = 3.14 (pi) * the diameter</b>. | ||
+ | |||
+ | <ul> | ||
+ | <li>Pi in Java has been provided for us through <b>Math.PI</b> </li> | ||
+ | <li> We also want to make sure we divide by 100.0 because our diameter is in centimeters right now as opposed to the meters we need to calculate the meters of development (if you remember!)<li> | ||
+ | <li>And finally, our constant will be a "final int double" to represent the circumference. We declare and calculate the circumference right away since we already know the diameter and we use a double to accommodate the decimal spaces | ||
+ | </ul> | ||
+ | |||
+ | <br/><br /> | ||
+ | Therefore our declaration becomes: | ||
+ | |||
+ | <pre> | ||
+ | final int double WHEEL_CIRCUMFERENCE = (70 * Math.PI)/100.0; | ||
+ | </pre> | ||
==Store user input on bicycle information== | ==Store user input on bicycle information== |
Revision as of 09:00, 31 March 2011
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ProblemYou are an employer on the software team of Bikers Forever, a bicycle company. The software team uses Java and the knowledge of the Java SDK to write programs for Biker Forever. You are a great COMP 1010 student so you already have an idea of writing in Java, so in breathless anticipation, you await your next assignment from the head of the software team :) You arrive at your desk on Monday morning and open your email in-box (as usual) to see this message from the head:
Hi <insert name here>,
Program Description
Formula
Output
You have entered 75 RPM and 20 rear teeth. Meters of development: 4.948008429403924 Speed [km/hour]: 22.266037932317655 Programmed by Bicycle Forever Date: September 18, 2008 *** End of Processing *** Thanks!, <insert name here>, I am confident you will do a great job. |
Cycling Speed | |
---|---|---|
SolutionTo program our solution, we will go through 4 steps:
In addition, we will be sure to comment through out our code, and follow correct programming standards as stated in [1]
Identify and declare all variables and constantsBased on The Boss's email to you, and the description of the program and formula, we can easily identify all the variables and constants important to the solution.
Declaration of Constants
final int FRONT_TEETH = 45; We also know the constant for the diameter is 70cm every-time. However, the diameter is not used in the calculations. Rather, the circumference is used to calculate the meters of development.
final int double WHEEL_CIRCUMFERENCE = (70 * Math.PI)/100.0; Store user input on bicycle informationThe code file contains more than one statements on each line. int digit1 = (isbn % 10);int total = digit1 * 9;isbn = isbn / 10; int digit2 = (isbn % 10);total = total + digit2 * 8;isbn = isbn / 10; Each of the above lines of code performs a similar function. Each line can be interpretted as a block of code. By placing each statements on a separate line and grouping the statements into appropriate code blocks, the result should look something like the following: int digit1 = (isbn % 10); int total = digit1 * 9; isbn = isbn / 10; int digit2 = (isbn % 10); total = total + digit2 * 8; isbn = isbn / 10; By placing each of the statements on a separate line, the readability of the code increases dramatically. Perform the calculationsOnce the statements are readable, the next step would be to organize them into code blocks as stated in COMP 1010 Coding Standards. Continuing with our previous example, the functionality of the code can be broken into two distinct code blocks. int digit1 = (isbn % 10); int total = digit1 * 9; isbn = isbn / 10; int digit2 = (isbn % 10); total = total + digit2 * 8; isbn = isbn / 10; Almost each line of code in the messy code file can be considered a separate code block. Take the time to read the code and understand how everything works together before deciding which statements should be grouped together. One of the code blocks that should be added is a variable declaration code block at the beginning of the main method. Throughout the messy code, integers are declared. All of the declaration statements should be placed at the beginning of the main method to ensure the code stays organized. Going to the previous example, two declaration statements can be moved to the top as depicted below. int digit1; int digit2; digit1 = (isbn % 10); int total = digit1 * 9; isbn = isbn / 10; digit2 = (isbn % 10); total = total + digit2 * 8; isbn = isbn / 10; Output the resultsAt the top of the main method, there should now be a number of variables declared. Notice that there are nine different "digit" variables which are only used once to store the same calculation. int digit1; int digit2; digit1 = (isbn % 10); int total = digit1 * 9; isbn = isbn / 10; digit2 = (isbn % 10); total = total + digit2 * 8; isbn = isbn / 10; The code sample from above shows two of the nine digit variables. These two variables can be replaced with a single one as follows: int digit; digit = (isbn % 10); int total = digit * 9; isbn = isbn / 10; digit = (isbn % 10); total = total + digit * 8; isbn = isbn / 10; Bonus Section: Outputting the Current DateThe messy code contained a total of eight different coding errors. Each error presented in this section is ordered as it appears in the code from the case study. Commenting and Testingint isbn = Temp; There are two problems with the above code sample. The first problem being that the variable "Temp" is of type string and not of the primitive type int. The second problem is the name of the variable "Temp". The variable was originally declared as "temp" and Java is a case sensitive language. Both programs are repaired by replacing the code with the line below. isbn = Integer.parseInt(temp); | ||
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