### Question:
StringUtil { public static boolean isBlank(String string) { return string == null || string.trim().isEmpty(); }  static boolean isBlank(String string); static Boolean isNotBlank(String string);  }### Answer:
@Test public void shouldCheckAStringForBlank() { assertThat(StringUtil.isBlank(""), is(true)); assertThat(StringUtil.isBlank(" "), is(true)); assertThat(StringUtil.isBlank(null), is(true)); assertThat(StringUtil.isBlank(" a "), is(false)); }