1、一般方法判断null值
if(country != null && country.getCity() != null && country.getCity().getSchool() != null && country.getCity().getSchool().getStudent() != null .....) { isValid = true;}
2、通过Optional判断null值
if (Optional.ofNullable(country) .map(Country::getCity) .map(City::getSchool) .map(School::getStudent) .isPresent()) { isValid = true;}
或
boolean isValid = Optional.ofNullable(country) .map(Country::getCity) .map(City::getSchool) .map(School::getStudent) .isPresent();
或
boolean isValid = Optional.ofNullable(country) .map(country -> country.getCity()) //Or use method reference Country::getCity .map(city -> city.getSchool()) .map(school -> school.getStudent()) .map(student -> true) .orElse(false);
3、使用Supplier
boolean isValid = isValid(() -> address, // first level () -> address.getCity(), // second level () -> address.getCountry(),// second level () -> address.getStreet(), // second level () -> address.getZip(), // second level () -> address.getCountry() // third level .getISO()@SafeVarargspublic static boolean isValid(Supplier
或
boolean isValid = isValid( Arrays.asList("address", "city", "country", "street", "zip", "Country ISO"), () -> address, // first level () -> address.getCity(), // second level () -> address.getCountry(),// second level () -> address.getStreet(), // second level () -> address.getZip(), // second level () -> address.getCountry() // third level .getISO() );@SafeVarargspublic static boolean isValid(List fieldNames, Supplier