Swing/BigDecimalSpinnerModel のバックアップ(No.5)

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) {
    Number v = getNumber();
    BigDecimal value  = new BigDecimal(v.toString());
    BigDecimal stepSize = new BigDecimal(getStepSize().toString());
    BigDecimal maximum  = new BigDecimal(getMaximum().toString());
    BigDecimal minimum  = new BigDecimal(getMinimum().toString());
    BigDecimal newValue;

    if(dir>0) {
      newValue = value.add(stepSize);
    }else{
      newValue = value.subtract(stepSize);
    }
    if(maximum != null && maximum.compareTo(newValue) < 0) {
      return null;
    }
    if(minimum != null && minimum.compareTo(newValue) > 0) {
      return null;
    }
    return newValue;
  }
}