Java Coding Problems

242. Confusing of() with ofNullable()

Confusing or mistakenly using Optional.of() instead of Optional.ofNullable(), or vice versa, can lead to weird behaviors and even NullPointerException.

Optional.of(null) will throw NullPointerException, while Optional.ofNullable(null) will result in Optional.empty.

Check the following failed attempt to write a snippet of code to avoid NullPointerException:

// Avoidpublic Optional<String> isbn(String bookId) {  // the fetched "isbn" can be null for the given "bookId"  String isbn = ...;  return Optional.of(isbn); // this throws NPE if "isbn" is null :(}

But, most probably, we actually wanted to use ofNullable(), as follows:

// Preferpublic Optional<String> isbn(String bookId) { // the fetched "isbn" can be ...