Strings should not be compared with ==
Remove unused imports
Prefer null to the empty string to indicate that the uid has not been set
The apiFormat variable is static - don't access it with "this"
Test that getItemRecTopN throws the correct exception when identify() has not been called
Implement Closeable to make it easier to use the client with Java 7 try-with-resources
Prefer declaring variables as Map rather than HashMap
The AsyncHttpClientConfig is only used in the constructor, convert to a local variable
Strings should not be compared with ==
Remove unused imports
Fix a couple of javadoc issues