WideFileInputInterpreter { @Nullable static Integer interpretBirthYear(@NotNull String birthYear) { if (birthYear.isEmpty()) { return null; } return Integer.parseInt(birthYear); } private  WideFileInputInterpreter();   }
@Test public void canInterpretBirthyear() { assertEquals(1960, (int) WideFileInputInterpreter.interpretBirthYear("1960")); assertNull(WideFileInputInterpreter.interpretBirthYear("")); }