6

DECIPHERING SECRET MESSAGES

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You’ve probably sent secret, encoded notes to your friends to try to hide the messages from your parents or teachers. In this chapter, we’ll be doing something similar as we create a Secret Messages app.

Our previous app, the Hi-Lo guessing game, was all about numbers—too high, too low, or just right. By contrast, our Secret Messages app will focus on text. You’ll learn to work with text strings and manipulate character values in Java to produce the encoded messages.

The Caesar Cipher

Our app will encode and decode secret messages using the Caesar cipher, an algorithm developed more than 2,000 years ago that uses ...

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