EngineHub
Replace the nullable annotations with guava's Optional class.
What's the point of Guava's Optional class?
Probably the single biggest disadvantage of null is that it's not obvious what it should mean in any given context: it doesn't have an illustrative name. It's not always obvious that null means "no value for this parameter" -- heck, as a return value, sometimes it means "error", or even "success" (!!), or simply "the correct answer is nothing". Optional is frequently the concept you actually mean when you make a variable nullable, but not always.
more: http://stackoverflow.com/questions/9561295/whats-the-point-of-guavas-optional-class
Optional class: http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/base/Optional.html
Example in com.sk89q.intake.argument.Namespace
/**
* Returns the value specified by the given key.
*
* @param key The key
* @return The value, which may be null, including when the key doesn't exist
*/
public Optional<Object> get(Object key) {
if (!locals.containsKey(key)) Optional.absent();
return Optional.of(locals.get(key));
}
/**
* Get an object whose key will be the object's class.
*
* @param key The key
* @param <T> The type of object
* @return The value
*/
@SuppressWarnings("unchecked")
public <T> Optional<T> get(Class<T> key) {
if (!locals.containsKey(key)) Optional.absent();
return Optional.of((T)locals.get(key));
}
I don't use Guava's Optional because it's not a proper monad and so you end up writing a lot of boilerplate code everywhere to deal with Optionals. I prefer Java 8's Optional, but it's too early to require Java 8 (plus optionals/monads are still a pain to work with prior to lambdas).
I was going to leave the ticket open in case there was a demand to switch over.
