Swing/BigDecimalSpinnerModel のバックアップ(No.18)

class BigDecimalSpinnerModel extends SpinnerNumberModel {
  public BigDecimalSpinnerModel(
      double value, double minimum, double maximum, double stepSize) {
    super(value, minimum, maximum, stepSize);
  }

  @Override public Object getPreviousValue() {
    return incrValue(-1);
  }

  @Override public Object getNextValue() {
    return incrValue(+1);
  }

  private Number incrValue(int dir) {
    BigDecimal value = BigDecimal.valueOf((Double) getNumber());
    BigDecimal stepSize = BigDecimal.valueOf((Double) getStepSize());
    BigDecimal newValue = dir > 0 ? value.add(stepSize) : value.subtract(stepSize);

    BigDecimal maximum = BigDecimal.valueOf((Double) getMaximum());
    if (maximum.compareTo(newValue) < 0) {
      return null;
    }

    BigDecimal minimum = BigDecimal.valueOf((Double) getMinimum());
    if (minimum.compareTo(newValue) > 0) {
      return null;
    }
    return newValue;
  }
}