CMPS 134 Fall 2024
Prog. Assg. #4: CSV Query Application
Due: Tuesday, Oct. 22

Background

Wikipedia describes CSV files as follows:

A comma-separated values (CSV) file is a delimited text file that uses a comma to separate values. Each line of the file is a data record. Each record consists of one or more fields, separated by commas. The use of the comma as a field separator is the source of the name for this file format. A CSV file typically stores tabular data (numbers and text) in plain text, in which case each line will have the same number of fields.

Although this does not seem to be standard terminology, we will use CSV-record to refer to a string that could play the role of a data record within a CSV file. That is, a CSV-record is a string that is intended to be interpreted as a sequence of fields, where each pair of consecutive fields is separated by a comma character (',').

The "class-list" files maintained by the University's Registrar are examples of CSV files. Each such file identifies the students who are enrolled in a particular section of a course and is accessible by the instructor of that course section. Each line/record in a class-list file is a CSV-record that describes a single student. Such a file looks something like this:

Example Class-List File

R01234567,Brown,Charlie,charlie.brown@scranton.edu,Freshman,Computer Science R45678912,Dinkley,Velma,velma@scoobydoo.com,Senior,Paranormal Crime R55555555,Neuman, Alfred E.,alfred.neuman@madmagazine.com,, R19283745,Van Pelt,Linus,linus.vanpelt@scranton.edu,Sophomore,Theology R98765432,Van Pelt,Lucy,lucy.vanpelt@scranton.edu,Junior,Chemistry

As you can infer, the fields in each line/record in a class-list file provide, respectively, a student's Royal Number, last name, first name and (possibly) middle initial, e-mail address, class, and major. The record describing Alfred E. Neuman illustrates that a field's value can be the empty string. (The last two fields in his record have that value.)

The use of the comma as the separator character is just a convention, as other characters (e.g., ;, $, #) could play the role just as well, depending upon what kind of entities are being described in the CSV file. In the ideal, one would choose as a separator a character that could not possibly occur within any field. If no such choice is possible, we can allow for the separator to occur within a field by using an escape sequence, similar to how Java uses \" to describe an occurrence of the double quote character within a literal string.

For the purposes of this assignment, we will follow convention by choosing the comma character (i.e., ',') as our separator and we will assume that it cannot occur within any field. We will break from convention by assuming that a comma appears not only between consecutive fields but also after the last field. This will make your life a little easier!

Specification

The CSV-records that can be queried by the program are those in a CSV-file whose name is provided to it via a command line argument (or what in jGrasp terminology is called a "run argument"). Initially, the CSV-record subject to being queried is the first record in the file. The user can advance from one record to the next by making an appropriate response at the prompt. Similarly, the user can quit at any time.

Sample User/Program Interaction

Example CSV-File

Smith,Karen,12 Main St.,Scranton,PA,18510,5'8",118,Blue, Jones,Brian,46 Elm St.,Springfield,IL,34567,6'1,202,Brown, Swift,Taylor,5 Brentwood,Hollywood,CA,98765,5'7,120,Blue,

Then here is one possible interaction with the program, with some explanatory notes to the right.

Interaction Explanation ----------- ----------- $ java CSVQuery person_data.csv Command-line invocation of program Enter query:>4 Asking for value of 4th field PA Enter query:>2 Asking for value of 2nd field 12 Main St. Enter query:>1 Karen Enter query:>N Asking to advance to next record Enter query:>7 202 Enter query:>0 Jones Enter query:>12 ? There is no 12th field Enter query:>N Enter query:>8 Blue Enter query:>6 5'7 Enter query:>Q Asking to quit Done!

Here are links to three other CSV-files that could serve you in testing your work: cartoon_chars.txt, Royals2024.txt, LadyRoyals2023.txt.