Exclude	Marks a field as excluded from the Database.
IgnoreExtraProperties	Properties that don't map to class fields are ignored when serializing to a class annotated with this annotation.
PropertyName	Marks a field to be renamed when serialized.
ThrowOnExtraProperties	Properties that don't map to class fields when serializing to a class annotated with this annotation cause an exception to be thrown.

ChildEventListener	Classes implementing this interface can be used to receive events about changes in the child locations of a given `DatabaseReference` ref.
DatabaseReference.CompletionListener	This interface is used as a method of being notified when an operation has been acknowledged by the Database servers and can be considered complete
Logger	This interface is used to setup logging for Realtime Database.
Transaction.Handler	An object implementing this interface is used to run a transaction, and will be notified of the results of the transaction.
ValueEventListener	Classes implementing this interface can be used to receive events about data changes at a location.

DatabaseError	Instances of DatabaseError are passed to callbacks when an operation failed.
DatabaseReference	A Firebase reference represents a particular location in your Database and can be used for reading or writing data to that Database location.
DataSnapshot	A DataSnapshot instance contains data from a Firebase Database location.
FirebaseDatabase	The entry point for accessing a Firebase Database.
GenericTypeIndicator<T>	Due to the way that Java implements generics (type-erasure), it is necessary to use a slightly more complicated method to properly resolve types for generic collections at runtime.
MutableData	Instances of this class encapsulate the data and priority at a location.
OnDisconnect	The OnDisconnect class is used to manage operations that will be run on the server when this client disconnects.
Query	The Query class (and its subclass, `DatabaseReference`) are used for reading data.
ServerValue	Contains placeholder values to use when writing data to the Firebase Database.
Transaction	The Transaction class encapsulates the functionality needed to perform a transaction on the data at a location.
Transaction.Result	Instances of this class represent the desired outcome of a single run of a `Transaction.Handler`'s doTransaction method.

Logger.Level The log levels used by the Realtime Database library

DatabaseException This error is thrown when the Firebase Database library is unable to operate on the input it has been given.