Java-Code

package de.trainyourprogrammer.java13;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * Calculate the 15th step with the following pattern:
 * 
 * 1.) 112 2.) 2112 3.) 122112 ...
 * 
 * @author jsb
 */
public class Main {

	/**
	 * Execute the program.
	 * 
	 * @param args
	 *            Is ignored in our case.
	 */
	public static void main(String[] args) {
		String input = "";

		System.out.println("Geben Sie eine Folge ein:"); // print the request

		BufferedReader buffer = new BufferedReader(new InputStreamReader(
				System.in)); // start reading from the default input

		try { // try to...
			input = buffer.readLine();
		} catch (IOException e) { // ignore occurring IOExceptions
		} finally { // on quit...
			try { // try to...
				buffer.close(); // stop reading the input
			} catch (IOException e) { // again ignore occurring IOExceptions
			}
		}

		String out = getNext(input); // get the row for the input

		for (int counter = 0; counter < 15; counter++) {
			System.out.println(out); // print the row
			out = getNext(out); // get the next row
		}
	}

	/**
	 * Helper method to get the next row of a given String.
	 * 
	 * @param row
	 *            The String to get the row from.
	 * 
	 * @return The next row.
	 */
	private static String getNext(String row) {
		String result = ""; // initialise the result
		char current; // initialise the char storing the currently counted digit

		try {
			current = row.toCharArray()[0]; // set the current digit to the
											// first
											// digit of the former row
		} catch (ArrayIndexOutOfBoundsException e) {
			current = 0; // if that fails set the current digit to null
		}

		int counter = 0; // initialise the counter

		for (char digit : row.toCharArray()) { // for every char in the row...
			if (digit != current) { // check if the digit is still the same
				result = result + Integer.toString(counter) + current; // append
																		// to
																		// result
				current = digit; // set the next digit
				counter = 1; // reset the counter
			} else { // else...
				counter++; // increase the counter
			}
		}

		return result + Integer.toString(counter) + current; // return the
																// result
	}
}