code: public BigDecimal optBigDecimal(String key, BigDecimal defaultValue) {
  		try {
  			return this.getBigDecimal(key);
  		} catch (Exception e) {
  			return defaultValue;
  		}
  	}
docs: Get an optional BigDecimal associated with a key, or the defaultValue if
  there is no such key or if its value is not a number. If the value is a
  string, an attempt will be made to evaluate it as a number.
  
  @param key A key string.
  @param defaultValue The default.
  @return An object which is the value.