Java - Why do only some error-throwing methods require error handling?

Question

For example, why is it that ObjectOutputStream.close();, which can throw an IOException, requires error handling (either a try-catch block or a throws declaration) while Integer.parseInt(String s);, which can throw a NumberFormatException, does not?

Answer 1

It's part of the language by design. IOException is a checked exception, and NumberFormatException is an unchecked exception (because it is a subtype of RuntimeException).