Java Reference
In-Depth Information
being used, you can replace each character in the line one-by-one. A session with
this
Rot13Input
program might look like this:
% java com.davidflanagan.examples.basics.Rot13Input
> Hello there. Testing, testing!
Uryyb gurer. Grfgvat, grfgvat!
> quit
%
The
main()
method of Example 1-13 calls another method,
rot13()
, to perform
the actual encoding of a character. This method demonstrates the use of the primi-
tive Java
char
type and character literals (i.e., characters that are used literally in a
program within single quotes).
Example 1−13: Rot13Input.java
package com.davidflanagan.examples.basics;
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"...
break; // ...break out of loop
StringBuffer buf = new StringBuffer(line); // Use a StringBuffer
for(int i = 0; i < buf.length(); i++) // For each character...
buf.setCharAt(i, rot13(buf.charAt(i)));// ..read, encode, store
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
}
}
