### Question:
USPhoneValidator extends RegexValidator implements ValidationPolicy<String> { public static USPhoneValidator instance() { return instance; } private  USPhoneValidator(); static USPhoneValidator instance();  }### Answer:
@Test public void testPhoneValidator() throws Exception { USPhoneValidator validator = USPhoneValidator.instance(); assertTrue(validator.validate("800-555-1212")); assertTrue(validator.validate("1-800-555-1212")); assertTrue(validator.validate("8005551212")); assertTrue(validator.validate("+1800-555-1212")); assertTrue(validator.validate("(800)-555-1212")); assertTrue(validator.validate("(800)5551212")); assertTrue(validator.validate("+43 720 0101010")); assertFalse(validator.validate("555-1212")); assertFalse(validator.validate("925413201")); assertFalse(validator.validate("")); }