public void printEigenEnergy(int number) {
        double[] ee = getEigenEnergy();
        if (ee.length == 0) {
            System.out.println("No eigen states found :-(");
            return;
        }
        int count = Math.min(number, ee.length);
        for (int i = 0; i < count; i++) {
            System.out.println(Utils.erg2ev(ee[i]) * 1e3 + " meV");
        }
    }