//-----------------------------------------------------------------
// Insert standard header information here.
//-----------------------------------------------------------------
/* SimpleCaesar will implement a simple caesar cipher.
* It uses a character array, cipher, to contain the mapping for enciphering.
* The array is indexed 0..25 where each index represents the distance
* of the letter from the beginning of the alphabet.
* The magic "c - 'a'" that you see throughout the code is
* a convenient way of finding the distance a lowercase character
* is from the beginning of the alphabet.
*/
import cs1.Keyboard;
public class StartCaesar {
private final static int SIZE = 26; // 26 letters in alphabet
private static char[] cipher = new char[SIZE]; // one element per letter
// ---------------------------------------------------------------------
// main method
//
// User Input: amount of offset, as a positive integer
// String to be enciphered
// Program Output: String as enciphered
//
// REQUIRES STUDENT MODIFICATION
// Needs only three relatively minor changes to do the basic task.
// Needs additional code to determine if there is
// another String to be encrypted, and to act accordingly.
//
// ---------------------------------------------------------------------
public static void main(String[] args)
{ int offset; // the KEY for how much to shift
String plain; // the original plaintext message
// ----- GET THE "KEY" TO USE (i.e., the offset value) -----
System.out.println("\tRevise the program so it will ask the user to "); // omit when done
System.out.print("Enter the encryption key to use: ");
offset = 0; // modify to obtain user input; limit it to valid values, if you can
// ----- USE THE "KEY" (i.e., build cipher[]) -----
makeCipher(offset);
// ----- GET THE "PLAINTEXT" (i.e., the message to encode) -----
plain = getPlainText();
// ----- DISPLAY THE MESSAGE IN ITS SECRET FORM:
System.out.println("\n\tRevise the program so it will display "); // omit when done
System.out.println("The secret version of your text:");
showSecret(plain);
}
// ----- DEVELOP THESE METHODS and MODIFY COMMENTS APPROPRIATELY -----
// ---------------------------------------------------------------------
// check method
//
// in this demo, it just returns the letter it received
// in your program, it should check if the character it received
// - is a letter, then encode it (depending on whether it's lower or upper case)
// - is not a letter, simply return it, as the method currently does.
//
// REQUIRES STUDENT MODIFICATION
// ---------------------------------------------------------------------
public static char check (char c)
{ char temp;
temp = c;
return temp;
}
// ---------------------------------------------------------------------
// encode method
//
// in this demo, it just returns the letter it received
// in your program, it should accept a lower case letter, and return the
// secretly encoded version of that letter
//
// REQUIRES STUDENT MODIFICATION
// ---------------------------------------------------------------------
public static char encode (char c)
{ return c;
}
// ---------------------------------------------------------------------
// encodeUpper method
//
// in this demo, it just returns the letter it received
// in your program, it should accept an upper case letter, convert that
// to lower case, encode the lower case letter, convert
// that back to upper case, and return that letter
//
// REQUIRES STUDENT MODIFICATION
//
// Note: it is possible to do all of this work inside the encode() method.
// But you should use this method, to practice writing and calling methods.
// ---------------------------------------------------------------------
public static char encodeUpper(char c)
{ char temp;
temp = c;
return temp;
}
// ---------------------------------------------------------------------
// makeCipher method
//
// in this demo, it does nothing
// in your program, it should create the cipher[] array, to hold the
// letters to substitute for each character in plain text
// note that it will have to handle both offset keys in [0, 25] (simple)
// and ones outside that range (Hint: % is again useful,
// but it's not sufficient on its own to achieve this.)
//
// REQUIRES STUDENT MODIFICATION
// ---------------------------------------------------------------------
public static void makeCipher(int key)
{ key = key;
}
// ---------------------------------------------------------------------
// getPlainText method
//
// THIS METHOD IS A "HACK" -- PLEASE USE THIS CODE AS-IS. DO NOT MODIFY IT!
//
// Because the Keyboard class is slightly brain-damaged,
// and may think it's reached the end of our String before its real end,
// we keep reading pieces and appending them to the previous input
// until the users *clearly* indicate the end of their input
// (i.e., for those who care, since K.readString() returns a null string
// at the end of the input, we copy until the read results in "null").
// REPEAT: 101-STUDENTS SHOULD USE THIS METHOD AS PROVIDED BY THE INSTRUCTOR.
// ---------------------------------------------------------------------
public static String getPlainText()
{ String s, text; // we need local versions of these vars
System.out.println("Enter your plaintext, and end with ^D (or ^Z on DOS):");
text = new String("");
do
{ s = Keyboard.readString();
if ( s != null )
{
// Append the new line to the text string.
// Also append a newline ('\n') character
// to replace the one that Keyboard.readString() consumes
text = text + s +'\n';
}
} while ( s != null );
return text;
}
// ---------------------------------------------------------------------
// showSecret method
//
// This method reads through the input one character at a time,
// sends each character off to be encoded, and then prints the
// character returned from the encoding process.
//
// Since, at the moment, the encoding methods do nothing,
// at the moment, this simply returns the original message.
// Once you get the earlier methods working, you should be able to
// just use this method as-is (i.e., all the changes go above).
// ---------------------------------------------------------------------
public static void showSecret(String text)
{
char c; // a temporary character variable
for(int i=0; i < text.length(); i++) // for each character in the input
{ c = check(text.charAt(i)); // GET ENCODED LETTER INSTEAD OF ORIGINAL
System.out.print(c); // print out the letter
}
}
}