Checker { public static boolean isBlank(String value) { return value == null || value.trim().length() == 0; } private  Checker(); static boolean isNullOrEmpty(T[] array); static boolean isNullOrEmpty(Collection<?> collection); static boolean isNullOrEmpty(Map<?, ?> map); static boolean isNullOrEmpty(String value); static boolean isBlank(String value); @Deprecated static boolean equals(Object a, Object b);  }
@Test public void testIsBlank() { assertTrue(Checker.isBlank(null)); assertTrue(Checker.isBlank("")); assertTrue(Checker.isBlank(" ")); assertTrue(Checker.isBlank(" ")); assertTrue(Checker.isBlank(" \n \t \r \f ")); assertFalse(Checker.isBlank("test")); }