CaesarChiffre.java

	public static String decrypt(String s) {
		StringBuffer res = new StringBuffer();
		for( int i = 0; i < s.length(); i++){
			res.append((char)(s.charAt(i) - 3));
		}
		return res.toString();
	}

KD.java

public class KD {
	/**
	 * Parse a "Klammerdarstellung" (KD) of a tree.
	 * 
	 * <ul>
	 * <li>An empty tree is encoded as '-'.</li>
	 * <li>A node is encoded as an uppercase letter, i.e. everything accepted by {@link Character#isUpperCase(char)}.</li>
	 * <li>Children are appended to the father as a ','-separated list of nodes enclosed in round brackets.</li>
	 * </ul> 
	 * 
	 * @param kd Tree encoded in KD
	 * @throws ParseException if the given String is not a valid KD of a tree.
	 */
	static int counter = 0;
	static String input = "";
	public static void parse(String kd) throws ParseException
	{
		counter = 0;
		input = kd;
		baum();
		if(counter < input.length()) throw new ParseException("nicht bsi ans ende", counter);
	}
	private static void baum() throws ParseException{
		knoten();
		if(outOfBoundCheck() && (char)(input.charAt(counter))=='('){
			counter ++;
			nachfolger();
			if(outOfBoundCheck() && (char)(input.charAt(counter))==')'){
				counter++;
			}
			else throw new ParseException("Missing closing bracket", counter);
		}
	}
	private static boolean outOfBoundCheck(){
		return input.length()>counter;
	}
	private static void nachfolger() throws ParseException{
		baum();
		while(outOfBoundCheck() && (char)(input.charAt(counter)) == ','){
			counter++;
			baum();
		}
	}
	private static void knoten() throws ParseException{
		if(outOfBoundCheck() && (char)(input.charAt(counter)) <= 'Z' && (char)(input.charAt(counter)) >= 'A' || outOfBoundCheck() && (char)(input.charAt(counter)) == '-' && counter > 0){
			counter ++;
		}
		else throw new ParseException("Nicht erlaubtes Knotenzeichen", counter);
	}

}