School Years
Write a program contained in a single file named "SchoolYears.java" that displays
a message telling the educational level of a student based on his/her number of
years of school. The user should be prompted to enter an integer indicating the
number of years of school, and the program should then print the corresponding
message given below.

    If years of school is      Then the message should be
    less than 0                The years in school must be a non-negative integer.
    0                          Education level:  No school
    1 - 5                      Education level:  Elementary school
    6 - 8                      Education level:  Middle school
    9 - 12                     Education level:  High school
    > 12                       Education level:  College

You may assume that the user will always enter an integer.  Be sure to keep your
logical expressions as simple as possible.  You will lose points if they are
unnecessarily complex (no compound 'if' statements should be used).  Also, for
this program you must use named global constants for all numbers other than zero.
In other words, no number other than zero should appear in 'main' or in any of
the other methods in your program.  Make sure your program contains no more than
four named constants, which should be named using all capital letters.

You may not use any global variables for this assignment.  Your program should
contain exactly two methods (in addition to 'main').  One of the methods should
be named "getYears" and should get the number of school years from the user.
The other method should be named "showSchool" and should display the appropriate
school level to the user.  Both of these methods must be called from 'main'.
Your program's output should be neat, organized, and grammatically correct,
similar to what is shown below.


Sample Output #1
Enter the number of years in school:    7
Education level:  Middle school

Sample Output #2
Enter the number of years in school:    12
Education level:  High school

Sample Output #3
Enter the number of years in school:    -4
The years in school must be a non-negative integer.


Advanced Option
Instead of asking for the number of years in school just one time, have
your program ask for a number of years, display the proper output, then
ask for another number of years, then display the correct output, then ask
for more years, and so on.  Keep doing this until the user presses the
ENTER key without entering any data at all.  In addition, after the user
presses the ENTER key by itself to quit the program, display a small table
showing the number of times that each level of education was displayed,
along with the percent value of the total number of entries.  Make sure
the values are nicely aligned in neat columns and the percent values are
rounded to one decimal place.