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CaesarCipher.java
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77 lines (68 loc) · 2.91 KB
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package stathis.Week1;
import edu.duke.*;
public class CaesarCipher {
public String encrypt(String input, int key) {
//Make a StringBuilder with message (encrypted)
StringBuilder encrypted = new StringBuilder(input);
//Write down the alphabet
String alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
String lalphabet = "abcdefghijklmnopqrstuvwxyz";
//Compute the shifted alphabet
String shiftedAlphabet = alphabet.substring(key)+ alphabet.substring(0,key);
String shiftedLAlphabet = lalphabet.substring(key)+ lalphabet.substring(0,key);
//Count from 0 to < length of encrypted, (call it i)
for(int i = 0; i < encrypted.length(); i++) {
//Look at the ith character of encrypted (call it currChar)
char currChar = encrypted.charAt(i);
if(Character.isLowerCase(currChar)){
int idx = lalphabet.indexOf(currChar);
if(idx != -1){
char newChar = shiftedLAlphabet.charAt(idx);
encrypted.setCharAt(i, newChar);
}
}
else{
//Find the index of currChar in the alphabet (call it idx)
int idx = alphabet.indexOf(currChar);
if(idx != -1){
//Get the idxth character of shiftedAlphabet (newChar)
char newChar = shiftedAlphabet.charAt(idx);
//Replace the ith character of encrypted with newChar
encrypted.setCharAt(i, newChar);
}
}
//If currChar is in the alphabet
//Otherwise: do nothing
}
// System.out.println(encrypted.toString());
//Your answer is the String inside of encrypted
return encrypted.toString();
}
public String encryptTwoKeys(String input, int key1,int key2){
StringBuilder encrypted = new StringBuilder(input);
String result = "";
for (int i = 0; i<encrypted.length(); i++){
if(i%2 == 0){
String temp3 = Character.toString(encrypted.charAt(i));
String temp1 = encrypt(temp3, key1);
result = result + temp1;
}
else{
String temp4 = Character.toString(encrypted.charAt(i));
String temp2 = encrypt(temp4,key2);
result = result + temp2;
}
}
System.out.println(result);
return result;
}
public void testCaesar() {
int key = 17;
FileResource fr = new FileResource();
String message = fr.asString();
String encrypted = encrypt(message, key);
System.out.println(encrypted);
String decrypted = encrypt(encrypted, 26-key);
System.out.println(decrypted);
}
}