COMP 14-090 Summer I 2000

Description

This assignment will use the skills of reading from a text file, taking command-line arguments, and manipulating an array of doubles. The text file to read from will be given as a command-line argument.  Open the text file and read in the first number, which will be an integer.  This number will tell you how many doubles are in the file.  Read in each double into a single array.  Print out the name of the file you read, the contents of the array, and the results of the following operations:

• find the minimum value
• find the maximum value
• compute the sum
• compute the average
• compute the running total
• compute the square (not square root) of each number
• compute the variance - (average of the squares - square of the average)
• compute the standard deviation - (the square root of the variance)

Hints

• For computing the square of each number and the running total, you'll have to create new arrays to hold the results.
• Running total -- for example, if the array was 1, 2, 3, the running total would be an array that contained 1, 3, 6.
• For computing the standard deviation, use Math.sqrt(), which takes a double as a parameter and returns its square root.
• Use methods that you've already written instead of re-writing code.  For example, calculating the average could call the calculate sum method to return the sum before dividing.  The variance method can also make much use of previously written methods.
• We'll cover reading text files in class today (Thursday), so there will be an example in the notes and on the course web page.
• For an example of handling command-line arguments, look at Listing 6.6 (NameTag.java) on page 281 of your textbook.
• Since the ArrayCalc class holds no state, all of the methods can be declared as static.  This also means that you don't have to instantiate an object of the class, just use the methods by their name and parameters (example: sum = calcSum (numbers); ).

What to Turn In

• A printout of your Java source code.
• A disk with your Java source code (ArrayCalc.java) and bytecode (ArrayCalc.class).
• An image of the output window. Make sure you see "==> End of job" before you capture the image. (You may include the output window image in the same document as your memo instead of turning in a separate printout of the output window.)
• A memo describing the problem and your solution of it. Include any problems you encountered or comments you may have about the assignment. Also, include an estimate of the total amount of time you spent working on this assignment.

1. Follow the instructions in Getting Started with Visual J++ under "Creating a New Project."  Use Assignment6 as your project name.
2. Follow the instructions under "Adding a New Class."  Name your class ArrayCalc.
3. Write in English the algorithm that you would use to complete this assignment.
4. Take each part one at a time and convert that to Java.
5. To run the program with a command line argument, select Assignment6 Properties... from the Project menu.  The window that pops up is below.  Pick Custom then type the command line arguments (put complete filename in quotation marks) after ArrayCalc in the Arguments box.  Make sure that the Program box says JView.exe and not WJView.exe

• Don't forget to comment your program! If there are no comments, you will lose at least 20% of the points.
• Don't forget to virus check and label your disk according to the instructions in Turning in Assignments on Disk.
• Don't forget to sign the pledge on the printout of your source code.
• Extra Credit will be given for printing out the sorted array (using either selection sort or insertion sort).
  10 points ascending order (lowest to highest)
  15 points descending order (highest to lowest)
  20 points both

The following output window is just an example. You don't have to use the same formatting. To get black text on a
white background, I pasted the captured image into the Paint program and inverted the colors.

The input file for the following example contained:

7
99.8
67.8
88.4
76.2
101.4
89.6
94.3

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