### Question:
AccountNumber implements Serializable, Formattable, Comparable<AccountNumber> { @Override public void formatTo(Formatter formatter, int flags, int width, int precision) { formatter.format("%s-%s", value / 1000, value % 1000); } private  AccountNumber(int value); static AccountNumber of(Integer value); @Override boolean equals(Object obj); @Override int hashCode(); @Override String toString(); @Override int compareTo(AccountNumber o); @Override void formatTo(Formatter formatter, int flags, int width, int precision); Integer toDatabaseValue();  }### Answer:
@Test public void formatTo() { assertEquals("123-123", String.format("%s", AccountNumber.of(123123))); assertEquals("1234-321", String.format("%s", AccountNumber.of(1234321))); }