Fix Java code generation for lookup URI methods

[helin24]

The java generation for type (string|Null)[] was creating @return one of <code>List<String></code> or <code>ElementList<Null></code>

see example:

@SuppressWarnings({"WeakerAccess", "unused"})
public class UriList extends Response {
 
  public UriList(JsonObject json) {
    super(json);
  }
 
  /**
   * A list of URIs.
   *
   * @return one of <code>List<String></code> or <code>ElementList<Null></code>
   */
  public Object getUris() {
    final JsonObject elem = (JsonObject)json.get("uris");
    if (elem == null) return null;
 
    if (elem.get("type").getAsString().equals("String")) return new String(elem);
    if (elem.get("type").getAsString().equals("Null")) return new Null(elem);
    return null;
  }

My change is the simplest thing I could think of, just making the return type List<String> instead and allowing some of the elements to be null. But I'm happy to implement something else if someone has a suggestion for a better type (along with how to get the generate code to produce it)

[bkonyi]

I don't think I can merge GitHub PRs directly into the SDK. We'll probably need to review this through Gerrit (the command to create a Gerrit review is git cl upload).

[helin24]

Oh I see, I will try that. Thanks!

[devoncarew]

I think it can be reviewed and merged through here?

https://dart-review.googlesource.com/c/sdk/+/231740

[bkonyi]

I think it can be reviewed and merged through here?

https://dart-review.googlesource.com/c/sdk/+/231740

Ah, yup! That should work.