class DenseMatrix extends Matrix {

  @Override
  public String toString() {
    final DecimalFormat format = FormatUtils.getDefaultDecimalFormat();
    final StringBuilder builder = new StringBuilder();

    this.forEach(
        (r, c, v) -> {
          if (0 != r && 0 == c) {
            builder.append(System.lineSeparator());
          }

          if (0 != c) {
            builder.append(" ");
          }

          builder.append(format.format(v));
        });

    return builder.toString();
  }

  public  DenseMatrix(final int rows, final int cols);
  public  DenseMatrix(final int rows, final int cols, final double[] values);

}