Problem Statement:
Sample files of city, state, zip code and other information were broken down into
several smaller files for emailing.  These are stored in several sequentially numbered
binary files within Lab3Data.zip that you can download from MyCourses. Your job is
to write a program that reads as many files as exist.  As you read each record load
only the city names into an ArrayList, and write a subset of what you read in into
another file containing only a few fields from the record.  Input and output file details
are given below.
You are writing this program to show the feasibility of the processing above, which
will be done on a much larger scale with world wide city, state and postal codes.  For
speed, you are to create one thread per file being read.  For example: the filenames
are in the format Lab3FileN.dat, where N starts with 1.  So for the first file you create
a thread object that reads in Lab3File1.dat, file number 2 a thread is created to
process Lab3File2.dat, and so on until your program discovers that some file does
not exist.
Once the files are all read in, the ArrayList is created, and the output file
ZipCityState.dat is created, write out how many cities were stored in the ArrayList,
and how many records were written to the new binary file.