code: @Override
      public void setRoundingMode(int roundingMode) {
          if (roundingMode < BigDecimal.ROUND_UP || roundingMode > BigDecimal.ROUND_UNNECESSARY) {
              throw new IllegalArgumentException("Invalid rounding mode: " + roundingMode);
          }
  
          this.roundingMode = roundingMode;
          resetActualRounding();
      }
docs: Sets the rounding mode. This has no effect unless the rounding increment is greater
  than zero.
  
  @param roundingMode A rounding mode, between <code>BigDecimal.ROUND_UP</code> and
  <code>BigDecimal.ROUND_UNNECESSARY</code>.
  @exception IllegalArgumentException if <code>roundingMode</code> is unrecognized.
  @see #setRoundingIncrement
  @see #getRoundingIncrement
  @see #getRoundingMode
  @see java.math.BigDecimal