public static Date parseDate(String datetimeStr) {
        if (StringUtils.isEmpty(datetimeStr)) {
            return null;
        }
        datetimeStr = datetimeStr.trim();
        if (datetimeStr.contains("-")) {
            if (datetimeStr.contains(":")) {
                datetimeStr = datetimeStr.replace(" ", "T");
            }
        } else if (datetimeStr.contains(":")) {
            datetimeStr = "T" + datetimeStr;
        }

        DateTime dateTime = new DateTime(datetimeStr, dateTimeZone);

        return dateTime.toDate();
    }
@PrepareForTest(StringUtils.class)
  @Test
  public void parseDateInputNotNullOutputNull() throws Exception {

    // Setup mocks
    PowerMockito.mockStatic(StringUtils.class);

    // Arrange
    final String datetimeStr = "a/b/c";
    final Method isEmptyMethod =
        DTUMemberMatcher.method(StringUtils.class, "isEmpty", String.class);
    PowerMockito.doReturn(true)
        .when(StringUtils.class, isEmptyMethod)
        .withArguments(or(isA(String.class), isNull(String.class)));

    // Act
    final Date actual = Util.parseDate(datetimeStr);

    // Assert result
    Assert.assertNull(actual);
  }