### Question:
USZipCodeValidator extends RegexValidator implements ValidationPolicy<String> { public static USZipCodeValidator instance() { return instance; } private  USZipCodeValidator(); static USZipCodeValidator instance();  }### Answer:
@Test public void testValidator() throws Exception { USZipCodeValidator validator = USZipCodeValidator.instance(); assertTrue(validator.validate("95120")); assertTrue(validator.validate("95120-1234")); assertFalse(validator.validate("450224")); assertFalse(validator.validate("")); }