CS 261 Assignment #0 (Optional)

Introduction:

The Assignment

Before coming up with the warning system, I needed to know if it was even feasible to tell if the freezer was working based on the power data I had available. How often does it run? How long does it run once it comes on? Could I tell the freezer's power consumption from other items on the same circuit? The graph below shows the power usage on the freezer's circuit on a recent afternoon as an example.

The tall spikes show when the freezer's using power. (The Y axis shows power in Watts, and it draws about 100 Watts when it's running.) It turns out there's only one other item on that circuit — some lights that, when turned on, use about 25 Watts. That's good news! Whether the lights are on or not, it's possible to detect the freezer running. (During the second peak the lights got turned on about 10 minutes after the freezer started running, and the lights were on already before the last two freezer runs shown.)

I've saved some data from the monitoring system, at one-minute intervals, and your job is to write a program that will report some basic stats on the freezer's power usage: How many minutes (on average) does it run each time it comes on? How many minutes are there between runs on average? And how much total power does it use over the monitored period?

Start by downloading and unzipping FreezerAsmt.zip. The project has a bit of starter code to help you get started. This project is short enough that it's fine with me if all of the code ends up in the main method, though you should feel free to break it into smaller pieces if you prefer. Note that the project folder also contains a file called data.txt holding a sample power-usage data file. Your finished program should prompt the user for the name of a data file, analyze the data in the file, then print a report. The output from my solution is shown below:

Please enter the filename to be analyzed 
data.txt
Thanks. Analyzing data in data.txt
Analyzed 2432 minutes of power data:
The freezer ran 36 times, for a total of 1.0466966716666664 kWh
The average run lasted 16.666666666666668 minutes
The average interval between runs was 50.888888888888886

Here are some more specific requirements:

• Your program should not assume that the file exists.
• If the file does exist, your program should produce appropriate output even if the file is empty, or if the freezer never runs.
• If the data shows at least one freezer run, you should report the total power usage (in kilowatt hours), the length of the average run (in minutes), and the length of the average interval between freezer runs (in minutes).
• Power use during periods where the freezer isn't running but the lights are on (e.g. 2pm in the graph above) should not be included in the freezer's total power usage. It's OK to include the power from the lights if they're on at the same time as the freezer though (e.g. 1:45pm in the graph above).
• A freezer run should only be counted if you observe both the beginning and the end of the run. For example, if there was an additional "partial" freezer run going on when data.txt ended, the proper count would still be 36 runs. It's ok if you include power usage from incomplete runs in the total.

Style Guide

• No unused variables or commented-out code is left in the class
• All instance variables (fields) are used in more than one method (if not, make them local variables)
• Javadoc comment at the top of each class (/** ... */)
• All methods have Javadoc comments
• Specific values have been replaced with constants (i.e. no "magic numbers")
• Proper capitalization of variable, method, and class names
• Use of white space to separate different sections of your code
• Consistent and appropriate indentation

Grading

• [10] Uses specified input and outputs
• [10] Uses File and Scanner objects properly
• [20] Calculates results properly
• [10] Handles error cases properly
• [10] Style and commenting

Extras

• Calculate stats on the power used by the lights, as well as the freezer.
• Get more precise about the power used by the freezer: If the lights are on as well, subtract off their contribution.
• Ignore power usage from any partial freezer runs at the beginning or end of the file.
• Look into ways to tidy up the formatting of the numeric results so that they have a smaller and consistent number of digits after the decimal point.

Submitting