import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map.Entry;
import java.util.Scanner;

// Make an application which reads a file 1 byte at a time and encrypts it based on
// the algorithm covered in the lecture notes and writes the result to another file
// Then send me the file and encryption key and I'll decrypt it to see if you did it correctly

public class CaesarCypher {
	public static HashMap<String, Integer> alphabet = new HashMap<String, Integer>();
	public static void alphabetMap() {
//		String alpha = "abcdefghijklmnopqrstuvwxyz";
		alphabet.put("a", 1);
		alphabet.put("b", 2);
		alphabet.put("c", 3);
		alphabet.put("d", 4);
		alphabet.put("e", 5);
		alphabet.put("f", 6);
		alphabet.put("g", 7);
		alphabet.put("h", 8);
		alphabet.put("i", 9);
		alphabet.put("j", 10);
		alphabet.put("k", 11);
		alphabet.put("l", 12);
		alphabet.put("m", 13);
		alphabet.put("n", 14);
		alphabet.put("o", 15);
		alphabet.put("p", 16);
		alphabet.put("q", 17);
		alphabet.put("r", 18);
		alphabet.put("s", 19);
		alphabet.put("t", 20);
		alphabet.put("u", 21);
		alphabet.put("v", 22);
		alphabet.put("w", 23);
		alphabet.put("x", 24);
		alphabet.put("y", 25);
		alphabet.put("z", 26);
	}

	public static void main(String[] args) {
		FileReader myFileReader;
		try {
			Integer key = 3; //value must be 1-25
			myFileReader = new FileReader("input.txt");
			Scanner myScanner = new Scanner(myFileReader).useDelimiter("[a-zA-Z]");
			PrintWriter myPrintWriter = new PrintWriter("output.txt");

			while (myScanner.hasNext()) {
				String letter = myScanner.next();
				Integer index = alphabet.get(letter); //new letter's position in alphabet

				if (key + index > 26) { //If moving this letter would go beyond alphabet
					index = index + key - 26;
				}
				else {
					index = index + key;
				}

				for (Entry<String, Integer> entry : alphabet.entrySet()) { //Get letter found at new position
			        if (entry.getValue().equals(index)) {
			        	myPrintWriter.write(alphabet.get(entry.getKey()));
			        }
			    }

//				myPrintWriter.print(alphabet.get(index));
			}

			myScanner.close();
			myPrintWriter.close();
		}

		catch (FileNotFoundException e) {
			e.printStackTrace();
		}
	}
}