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VCipher.java
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VCipher.java
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/**
* Programming AE2
* Class contains Vigenere cipher and methods to encode and decode a character
*/
public class VCipher
{
private char [] alphabet; //the letters of the alphabet
private final int SIZE = 26;
private char [][] vcipher;
private int len;
/**
* The constructor generates the cipher
* @param keyword the cipher keyword
*/
public VCipher(String keyword)
{
len=keyword.length();
// create alphabet array
alphabet= new char [SIZE];
for (int i=0; i< SIZE; i++)
alphabet[i]=(char)('A'+i);
// find length of keyword for 1st dimension of array
// second dimension is the alphabet length (26)
vcipher=new char[len][SIZE];
// create VCipher array
for (int i=0; i<len; i++) {
int count=0;
// indexing the letters of keyword
char key=keyword.charAt(i);
for (int j=0; j< SIZE; j++) {
// create first part of VCipher
// first dimension of array= letters of the keyword
// second dimension of array= keyword char+1 to Z
if (j<'Z'-key+1) {
vcipher[i][j]= (char)(keyword.charAt(i)+j);
}
// create second part of VCipher
// remainder of the cipher= from A up to keyword char-1
else {
vcipher[i][j]=(char)('A'+count);
count++;
}
}
}
// print test for the vcipher array
for (int i=0; i<len; i++) {
for (int j=0; j<SIZE; j++) {
System.out.print (vcipher[i][j]);
}
System.out.println();
}
}
/**
* Encode a character
* @param ch the character to be encoded
* @return the encoded character
*/
public char encode(char ch, int counter)
{
for (int i=0; i<SIZE; i++) {
if (ch== alphabet[i]) {
return vcipher[counter%len][i];
}
}
return ch;
}
/**
* Decode a character
* @param ch the character to be decoded
* @return the decoded character
*/
public char decode(char ch, int counter)
{
for (int i=0; i<SIZE; i++) {
if (ch== vcipher[counter%len][i]) {
return alphabet[i];
}
}
return ch;
}
}