### Question:
PhoneNumberUtils { @Nullable public static Integer getCountryCode(String countryIso) { return countryIso == null ? null : CountryCodeByIsoMap.get(countryIso.toUpperCase(Locale.getDefault())); }  @Nullable static Integer getCountryCode(String countryIso);  }### Answer:
@Test public void testGetCountryCode() throws Exception { assertEquals(new Integer(86), getCountryCode(Locale.CHINA.getCountry())); assertEquals(null, getCountryCode(null)); assertEquals(null, getCountryCode(new Locale("", "DJJZ").getCountry())); }