### Question:
FinancialAmountUtil { public static BigDecimal addHandlingNulls(final BigDecimal amount, final BigDecimal amountToAdd) { if (amountToAdd == null) return amount; return amount == null ? amountToAdd : amount.add(amountToAdd); }  static BigDecimal subtractHandlingNulls(final BigDecimal amount, final BigDecimal amountToSubtract); static BigDecimal addHandlingNulls(final BigDecimal amount, final BigDecimal amountToAdd); static BigDecimal determineVatAmount(
            final BigDecimal netAmount,
            final BigDecimal grossAmount,
            final Tax tax,
            final LocalDate now); static BigDecimal determineNetAmount(
            final BigDecimal vatAmount,
            final BigDecimal grossAmount,
            final Tax tax,
            final LocalDate now); static BigDecimal determineGrossAmount(
            final BigDecimal netAmount,
            final BigDecimal vatAmount,
            final Tax tax,
            final LocalDate now);  }### Answer:
@Test public void addHandlingNulls() throws Exception { BigDecimal amount; BigDecimal amountToAdd; BigDecimal result; amount = new BigDecimal("100"); amountToAdd = new BigDecimal("10.11"); result = FinancialAmountUtil.addHandlingNulls(amount, amountToAdd); Assertions.assertThat(result).isEqualTo(new BigDecimal("110.11")); amount = new BigDecimal("100"); amountToAdd = null; result = FinancialAmountUtil.addHandlingNulls(amount, amountToAdd); Assertions.assertThat(result).isEqualTo(new BigDecimal("100")); amount = null; amountToAdd = new BigDecimal("10.11"); result = FinancialAmountUtil.addHandlingNulls(amount, amountToAdd); Assertions.assertThat(result).isEqualTo(new BigDecimal("10.11")); amount = null; amountToAdd = null; result = FinancialAmountUtil.addHandlingNulls(amount, amountToAdd); Assertions.assertThat(result).isNull(); }