Lab 4: Using arrays

The goal of this lab is to practice using arrays, including the args array.

1. Introduction

Your task in this lab is to write a program which receives as input a series of double values interpreted as the amount of rainfall in successive months. For example, if it were given twelve numbers

1.4 5.2 7.3 4.2 4.6 2.8 7.4 5.2 4.7 8.2 1.2 3.6

this would be interpreted as 1.4 units of rainfall in January, 5.2 in February, etc. You will be given several years' worth of data as one big long list of numbers. Your program will use this data to generate a table which gives for each month (1) the average rainfall for that month (over the years for which the data is given), (2) the rainfall for the most recent month, and (3) how much above or below average the most recent month is. The output will look something like

Jan     0.8210748805348682      0.6834390522400943      -0.13763582829477394
Feb     1.9194515641683012      1.5679950865951544      -0.3514564775731468
Mar     2.400285002785132       3.164213954524053       0.763928951738921
Apr     5.804738126602605       0.9830287758148275      -4.821709350787778
May     3.76182675153702        3.7344725369276395      -0.027354214609380367
Jun     3.403902173143365       2.9068214333763476      -0.4970807397670174
Jul     2.0318258917252052      1.9840330236370396      -0.04779286808816563
Aug     2.007361328245369       1.7773942658914221      -0.22996706235394693
Sep     3.7161954697495743      4.393987589988356       0.6777921202387818
Oct     5.0173608869616055      5.002715375175615       -0.014645511785990273
Nov     3.0615176722351523      3.063504430523706       0.0019867582885537693
Dec     2.447781305843466       2.7600102891290796      0.31222898328561355

2. Set up

Copy the following file from the course public directory:

cp /homeemp/tvandrun/pub/235/RainDataGen.class .

It is a program that generates random (within carefully defined ranges) of rainfall data for a random number (between 10 and 30) of years.

3. Your task

You are to write a program that does what is described above, which reads its data from the command line (from the args array). The following information should help you:

• You can test/run your program by doing

  java YourProgram `java RainDataGen`
  

  The `java RainDataGen` executes what's between the tick marks (that character is the left single quote, not an apostrophe, found on the same key as the tilde) tells the Unix shell first to execute java with the RainDataGen program, and then replace the string on the command line with the output of the program.
  
  
• You can assume that the number of items produced by RainDataGen (and therefore the number of elements in args) is a multiple of twelve, since you are receiving data for complete years. You don't know how many years you are getting (though you can always calculate that by taking the length of args and dividing by 12).
  
  
• You can use the operation Double.parseDouble() to convert from a String to a double. It takes a String (ie, between the parentheses) and results in a double. (Don't you wish you knew that last week?)
  
  
• The escape sequence \t is great for generating nice-looking tables.

4. To turn in

1. Start a script file.
2. Display the source file.
3. Compile
4. Run the program
5. Exit the script
6. Print out the script file. Use the command a2ps instead of lpr-- this make the file print in "two-up" form, that is, two pages per page. (a2ps -P sp typescript-- or whatever the name of your script file is)

Make sure you have exited the script file before you print, or else it will print forever!

Then turn in the hard copy to me.