The document outlines instructions for writing a Java program that converts letters of the alphabet into corresponding telephone digits using a while or do-while loop and a switch statement. The program accepts user input of letters from a to z, providing error messages for non-alphabetic characters, and terminates when '&' is entered. The letter-to-digit correspondence is specified, with groupings such as 'abc' for 2 and 'def' for 3.

1. Write a Java program using while loop or do -while and switch to convert letters of the alphabet
into their corresponding digits on the telephone. The program should let the user enter letters from
A to Z. An error message should be printed for any nonalphabetic character that is entered. When
the & is entered, the program will be terminated.
The letters and digits on the telephone have the following correspondence:
ABC = 2
DEF = 3
GHI = 4
JKL = 5
MNO = 6
PQRS = 7
TUV = 8
WXYZ = 9