Alphabetic Shift

Write a program that decodes secret messages read from a text file using an "alphabetic shift." So, for example, a shift might appear as:

ORIGINAL ABCDE...XYZ
SHIFTED. CDEFG...ZAB

You must:

1.) Read the encoded message from the attached MessageIn.txt file,
2.) Count the instance of each character in the file,
3.) The most common character in the message should be an "E". Use this information to calculate the amount of the shift,
4.) Print out the decoded message.

I am a beginner with Java and was needing help writing this program. If anybody could help at all it would be greatly appreciated.