Optionalを使って、NullPointerExceptionの発生を防ぐ。
import java.util.Optional;
public class Test {
public static void main(String[] args) {
String str = null;
// System.out.println(str.length()); // java.lang.NullPointerException
Optional<String> strOpt = Optional.ofNullable(str);
if(strOpt.isPresent()) {
String message = strOpt.get();
System.out.println(message.length());
}
strOpt.ifPresent(v -> System.out.println(v.length()));
}
}