very simple spaceship simulator

Spaceship.java

public class Spaceship {
	public int people = 10; // the amount of people living on the ship
	public int food = 100; // the amount of food the people can use for surviving
	public int fuel = 100; // how much fuel is left for flying
	public double[] cord = new double[2]; // coordinates of the ship - X,Y
	public double[] course = new double[2]; // coordinates of the flying target - X,Y
	
	public static void main(String[] args) {
		Spaceship traumschiffSurprise = new Spaceship(5.0, 4.0, 9.0, 9.0);
		int i = 1;
		while (traumschiffSurprise.advancetime()) {
			System.out.println("Tag " + i + " in ihrem Raumschiff.");
			System.out.println("Wir befinden uns im Moment bei diesen Vektoren:");
			System.out.println("x " + traumschiffSurprise.cord[0] + " | y " + traumschiffSurprise.cord[1]);
			System.out.println("Wir halten Kurs auf diese Vektoren:");
			System.out.println("x " + traumschiffSurprise.course[0] + " | y " + traumschiffSurprise.course[1]);
			System.out.println("Weitere Schiffsdaten:");
			System.out.println("Personen: " + traumschiffSurprise.people + " | Treibstoff: " + traumschiffSurprise.fuel + " | Essen: " + traumschiffSurprise.food);
			System.out.println("Geben sie n ein, um zu schlafen...");
			
			while (System.console().readLine().charAt(0) != 'n') {
				System.out.println("Geben sie n ein, um zu schlafen...");
			}
			
			i++;
		}
		System.out.println("Das Schiff ist explodiert, da keine Personen mehr leben.");
	}
	
	public Spaceship(double cordx, double cordy, double coursex, double coursey) {
		// if no valid values are submitted, standard values will be used
		if (cordx > 0 && cordx < 10 && cordy > 0 && cordy < 10 && coursex > 0 && coursex < 10 && coursey > 0 && coursey < 10) {
			this.cord[0] = cordx;
			this.cord[1] = cordy;
			this.course[0] = coursex;
			this.course[1] = coursey;
		} else {
			this.cord[0] = 5.0;
			this.cord[1] = 5.0;
			this.course[0] = 5.0;
			this.course[1] = 5.0;
		}
	}
	public boolean advancetime() {
		// advance one day in time
		// FIRST - fly if enough fuel (>= 10) is left
		if (this.fuel >= 10) {
			double[] newcord = calcnewcoords();
			this.cord[0] = newcord[0];
			this.cord[1] = newcord[1];
			// decrease amount of fuel by 10
			this.fuel -= 10;
		}
		// SECOND - let people eat and/or die
		if (this.food >= this.people) {
			// enough food for everyone
			this.food -= this.people;
		} else {
			// sorry for your loss
			this.people = this.food;
			this.food = 0;
		}
		// THIRD - explode if everyone is dead
		if (this.people == 0) {
			return false;
		}
		return true;
	}
	private double[] calcnewcoords() {
		// calculates new coords. isn't interested in fuel
		double[] direction = new double[2];
		// get direction vector
		direction[0] = this.course[0] - this.cord[0];
		direction[1] = this.course[1] - this.cord[1];
		// calculate length of vector using pythagoras
		double len = Math.sqrt(direction[0]*direction[0] + direction[1]*direction[1]);
		// make direction vector shorter so it has a len of 1
		direction[0] = direction[0] / len;
		direction[1] = direction[1] / len;
		// calculate new coords (store them in direction vector - evil!)
		direction[0] = this.cord[0] + direction[0];
		direction[1] = this.cord[1] + direction[1];
		return direction;
	}
}