### Question:
StringUtils { public static boolean isNullOrEmpty(String string) { return string == null || string.isEmpty(); } private  StringUtils(); static String padStart(String string, int minLength, char padChar); static boolean isNullOrEmpty(String string); static String padLeft(String value, int minLength);  }### Answer:
@Test void isNullOrEmpty() { assertThat(StringUtils.isNullOrEmpty("")).isTrue(); assertThat(StringUtils.isNullOrEmpty(null)).isTrue(); assertThat(StringUtils.isNullOrEmpty("hello")).isFalse(); assertThat(StringUtils.isNullOrEmpty(" ")).isFalse(); }