/** Encrypt and decrypt data using the Caesar cipher.
 *  For the purpose of this simple program, it's not necessary to keep
 *  around both the plaintext and ciphertext Strings, but if we enhance
 *  the program, they may be useful.
 * 
 *  The 'key' attribute is the number we need to add to each letter to
 *  encrypt it.
 */

public class Caesar implements Encryption
{
  // private String plaintext;
  // private String ciphertext;
  private static int key = 7;


  /** encrypt -- Go through each character of the string and add the key
   *  value.  Note that the cast is needed because the + operator returns 
   *  an integer result.
   */
  public void encrypt(String plaintext)
  {
    String ciphertext = "";
    for(int i = 0; i < plaintext.length(); ++i)
      ciphertext += (char) (plaintext.charAt(i) + key);
    System.out.println(ciphertext);
  }

  /** decrypt -- this is exactly the inverse of encrypt
   */
  public void decrypt(String ciphertext)
  {
    String plaintext = "";
    for (int i = 0; i < ciphertext.length(); ++i)
      plaintext += (char) (ciphertext.charAt(i) - key);
    System.out.println(plaintext);
  }
}