Caesar Cipher

caesarcipher.java

import acm.program.*;

public class Caesar extends ConsoleProgram {
  
	private char encryptChar (char ch, int key){
		if (Character.isUpperCase(ch)) {
			return((char)('A' + ((ch - 'A' + key)%26)));
		}
		return ch;
	}
	
	private string encryptString (string str, int key) {
		if (key<0){
			key = 26 - (-key % 26);
		} 
		string encrypted = "";
		for (int i = 0; i < str.length; i++){
			char ch = str.charAt(i);
			result += encryptChar (ch, key);
		}
		return encrypted;
	}

	public void run() {
		int key = readInt ("Enter Key: ");
		string plaintext = readLine ("Enter Text: ");
		string cipher = encryptString(plaintext, key);
		println(cipher);
	}


}