// This example is from _Java Examples in a Nutshell_. (http://www.oreilly.com)
// Copyright (c) 1997 by David Flanagan
// This example is provided WITHOUT ANY WARRANTY either expressed or implied.
// You may study, use, modify, and distribute it for non-commercial purposes.
// For any commercial use, see http://www.davidflanagan.com/javaexamples
import java.io.*; // We're doing input, so import I/O classes
/**
* This program reads lines of text from the user, encodes them using the
* trivial "Rot13" substitution cipher, and then prints out the encoded lines.
**/
public class Rot13Input {
public static void main(String[] args) throws IOException {
// Get set up to read lines of text from the user
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
for(;;) { // Loop forever
System.out.print("> "); // Print a prompt
String line = in.readLine(); // Read a line
if ((line == null) || line.equals("quit")) // If EOF or "quit" then...
break; // ... break out of the loop
StringBuffer buf = new StringBuffer(line); // Convert to a StringBuffer
for(int i = 0; i < buf.length(); i++) // For each character...
buf.setCharAt(i, rot13(buf.charAt(i))); // read, encode, put it back
System.out.println(buf); // Print encoded line
}
}
/**
* This method performs the Rot13 substitution cipher. It "rotates"
* each letter 13 places through the alphabet. Since the Latin alphabet
* has 26 letters, this method both encodes and decodes.
**/
public static char rot13(char c) {
if ((c >= 'A') && (c <= 'Z')) { // For uppercase letters
c += 13; // Rotate forward 13
if (c > 'Z') c -= 26; // And subtract 26 if necessary
}
if ((c >= 'a') && (c <= 'z')) { // Do the same for lowercase letters
c += 13;
if (c > 'z') c -= 26;
}
return c; // Return the modified letter
}
}
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