Based on what you're trying to do here, it looks like the problem is that you're trying to map the response from this API endpoint to the ResultSet class. I expect that this map is failing, because this endpoint returns a single object, with a set of properties containing information about the account. You can see an example of the class we use in our Java SDK for mapping the response from this endpoint here: https://github.com/constantcontact/java-sdk/blob/master/src/main/java/com/constantcontact/components...
If that doesn't solve the problem, please let us know!
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