My solution to @code_of_duty challenge

Cod.java

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintStream;

/**
 * Proposed solution to Code of Duty
 * @author adrienjoly
 * This program is dedicated to Anouck ^^
 **/
public class Cod {
	
	protected static PrintStream os = System.out;
	
	protected int vect[];
	protected int i = 0, sum = 0, iter = 0;
	
	/**
	 * Initialize a vector of given size
	 * @param size
	 */
	public Cod (int size) {
		vect = new int[size];
	}
	
	/**
	 * Add n as the next number of the vector
	 * @param n
	 */
	public void feed (int n) {
		vect[i++] = n;
		sum += n;
	}
	
	/**
	 * Print the current state of the vector
	 */
	public void printVect() {
		os.print((iter++) + " : (");
		for (int i=0; i<vect.length-1; ++i)
			os.print(vect[i] + ", ");
		os.println(vect[vect.length-1] + ")");
	}
	
	/**
	 * Process the vector, and print iterations
	 */
	public void printIterations() {
		if (sum % vect.length != 0) // check if the vector is balanced
			os.println(-1);
		else {
			// build a difference vector
			int diff[] = new int[vect.length-1];
			int goal = sum / vect.length; // goal is the expected value for all items
			int prev = 0, iterations = 0;
			
			for (int i=0; i<diff.length; ++i) {
				prev = diff[i] = vect[i] - goal + prev;
				iterations = Math.max(iterations, Math.abs(diff[i]));
			}
			
			os.println(iterations);
			printVect();
			
			// process the vector
			for (int remain = iterations; remain > 0; --remain) {
				// process left-to-right transfers, for positive diff values
				for (int i=0; i<diff.length; ++i) {
					if (diff[i] > 0 && vect[i] > 0) {
						--vect[i];
						++vect[i+1];
						--diff[i];
					}
				}
				// process right-to-left transfers, for negative diff values
				for (int i=diff.length-1; i>=0; --i) {
					if (diff[i] < 0 && vect[i+1] > 0) {
						--vect[i+1];
						++vect[i];
						++diff[i];
					}
				}
				printVect();
			};
		}
		os.println();
	}
	
	public static void main(String[] args) throws NumberFormatException, IOException {
		
		BufferedReader reader = new BufferedReader(new FileReader("input.txt"));
		os = new PrintStream("output.txt");
		
		String line;
		Cod current = null;
		
		while ((line = reader.readLine()) != null) {
			if (null == current) // initialize a new vector, given its length
				current = new Cod (Integer.parseInt(line));
			else if (line.length() == 0) { // empty line => process the vector
				current.printIterations();
				current = null;
			}
			else // in between: feed the vector with sequence of int
				for (String n : line.split(" "))
					current.feed(Integer.parseInt(n));
		}
	}
}