Hi XiangCheng,
You can get your api_key in your account at
https://bigml.com/account/apikey and as a tip you have available a "shortcut" to make queries directly to BigML's API (
bigml.io) on each screen of the web page. See the attached picture to she what I'm talking about.
By the way, the listDataset(…) method expects a query string like parameter. So, I think that you want to retrieve your datasets with the name "Iris", then the string parameter should be something like "name=Iris". But if you want to be less strict in the query, you may want to include the "icontains" parameter in the query string, then the listDatasets(…) call would be:
JSONObject listing = BigMLClient.getInstance(true).listDatasets( "name__icontains=iris" );
Please, let us know if that fixes your issue.
Oscar Rovira
Software Engineer | BigML Inc.