CISC370, Homework H02, Summer 2007
Basic Java Skills

Due: Tuesday 06/19, 11:55pm

Better: Do half tonight, half Wednesday night

Introduction

In this assignment, you'll create three small Java Programs.

These programs are not necessarily very object oriented—they will mostly be small programs consisting of a class with a public static void main method, and perhaps one or two other public static methods. The purpose is to get you used to programming in Java, and to get you up to speed on some of the basics such as:

• accessing command line parameters
• simple input and output via stdin (e.g. the keyboard), and stdout (e.g. your terminal session)
• reading from and writing to files on the disk
• working with numbers and strings
• working with Math functions (e.g. trig functions, square root, etc.)
• working with arrays

You may collaborate—provided you document your collaboration

If you want to work together in teams of up to three people (you pick the teams) you may—or you may work individually.

If you work together...

A few rules for working together on this assignment:

• Even if you work together, for this assignment, each person must still script and submit separately.

  • That is a rule for this assignment only—in future assignments, I may change that rule.
  • It is ok, though, to share code provided you adhere to the rules below.

• Each person on the team should "take the lead" on at least one of the three programs. Indicate who took the lead on each one in the comments. You might write something like this:

  // H02a.java for CISC370, 06/13/07
  // Programmers: Ella Fitzgerald (Lead), Cassius Clay, Keith Richards 
  // Calculate height of a tree
  // ...

  // H02b.java for CISC370, 06/13/07
  // Programmers:  Keith Richards (Lead), Cassius Clay, Ella Fitzgerald
  // Count words in a file
  // ...

  // H02c.java for CISC370, 06/13/07
  // Programmers:  Cassius Clay (lead), Ella Fitzgerald, Keith Richards
  // Sort a list of integers
  // ...

• Be sure that you understand all of the code for each of the programs your team submits. There may be exam or quiz questions based on programming assignments—and if the quiz question is on the part of the assignment you didn't work on, and you didn't bother to review it in detail, you may be out of luck!

Required Reading

For this assignment, your best bet is to use an internet search engine, along with the many Java resources on the web.

Overview

What you need to do

In a directory on strauss called ~/cisc370/h02, create and test source code for each of three programs indicated below.

Create a single script in which, for each of the three programs, you cat the source code for the program, show that the program compiles, and then show that the program works properly.

Think carefully about your scripting strategy.

Note that for some programs, running it once may not be enough to show that it works properly. You may also need to

• do directory listing to show the presence or absence of input or output files
• cat input files before you run the program, or output files after you run the program
• run the program several times with different inputs (to show various error conditions that may occur)

You are responsible for using your intelligence and judgment to determine what is needed.

In a 300-level class, it is not the responsibility of the Instructor or TA to spell that out for you in detail. We are available to help you brainstorm, and if you submit a detailed clear test plan sufficiently in advance, we might be willing to sign off that it is enough testing, but this is not guaranteed.

H02a.java: A program to calculate the height of a tree

Write a program that helps a surveyor estimate the height of a tree (the green line) as shown in the picture below.

Inputs are the height of the leveling instrument, the angle theta (between level, and a sight-line to the top of the tree, in degrees), and the distance to the base of the tree.

Make simplifying assumptions as needed (i.e. level ground, the inaccuracy introduced by the thickness of the tree is insignificant to the measurement.) You may ask for measurements in feet or meters, as you see fit, but be sure to label your inputs and your outputs consistently with whatever unit you choose.

Use type double to represent all numeric values.

Things you will need to find out:

• how to do trig functions in Java
• how to input values of type double

H02b: Write a program to calculate the number of words in a file

Write a program that takes the name of a file on the command line as the first input parameter. Open that file, and read each line. Count the total number of words in the file, and print the total on the "standard output" stream.

Produce an error message if there is not exactly one input parameter, or if the file cannot be opened. Write that message to the "standard error" output stream, not the standard output stream.

Consider "words" to be any sequence of one or characters "non-white-space" characters, where "white space" is defined (for purposes of this exercise) as sequence of 1 or more of space, tab (\t), newline/line feed (\n), carriage return (\r), or form feed (\f) characters.

Things you need to find out:

• How to open an input file, and read a word at a time or a line at a time
• If you read a line at a time (which is probably the best approach), how to break up a line into words
• A way to test your program. (Hint: read the man page for the Unix command wc).

H02c: Write a program to sort a list of integers

Write a program that takes the name of two files on the command line as the first and second input parameters:

• the first should be an input file
• the second should be the name of an output file

The input file should consist of a sequence of integers, one per line. Your program should read every line in that file.

Your program should write an output file with the name given, consisting of the same integers, sorted, one per line.

Produce an error message if any of the following occur:

• there are not exactly two input parametesr,
• if the input file cannot be opened
• if the output file cannot be opened
• if the input file does not consist of exactly one integer per line

Things you need to determine:

• How to handle errors with input files in Java
• How to work with arrays, or other kinds of lists in Java
• The most effective way to sort.
  • Do you need to write the sort from scratch?
  • Or, is there already a sort routine built into Java? (If you can find one and determine how to use it, you may use it!)

Consider "words" to be any sequence of one or characters "non-white-space" characters, where "white space" is defined (for purposes of this exercise) as sequence of 1 or more of space, tab (\t), newline/line feed (\n), carriage return (\r), or form feed (\f) characters.

Finishing and Submitting: Create a tar or zip file, and turn it in on WebCT

Submit your work on WebCT for the assignment marked H02. Upload and submit BOTH

• a single H02.txt file, which is a script of your programs.
• a single H02.tar, H02.tar.gz or H02.zip file, containing all of your java source code, and where applicable, sample input files.
  • Your tar or zip files should NOT contain your .class files---remove these before creating your file.

If you do not know how to create a tar consult the following lab from CISC181 for an overview.

Reminder: Submit your code both in your .txt file and in your .tar file

A reminder: even though your H02.tar (or tar.gz, or .tgz. or .zip file) contains your Java source, you are still required to "cat" this source code in your .txt file, and submit it in both forms. If you do not, you will lose points.

Here's why: Submitting both allows your TA the ability to

• print one file (your .txt. file) and have some place to write comments on all of your code
• compile and run your code without having to tediously extract it from your script file.

Of course, the two should agree—if they don't, that's also a potential grading deduction. So if you make changes to your code, be sure that you redo both your script, and your tar/zip file.

Next Steps: Read Chapters 5-6 in HFJ

Now read Chapters 5-6 for Thursday. As you read, you may want to apply the typo corrections from the errata to your book.

Grading Rubric (180 pts total)

Due Date: (see top of file)