org.apache.zookeeper is composed of the interface definition for ZooKeeper watches and various callback handlers of ZooKeeper. It defines the main class of the ZooKeeper client library along with many static definitions of the ZooKeeper event types and states. The
org.apache.zookeeper.data package defines the characteristics associated with the data registers, also known as znodes, such as Access Control Lists (ACL), IDs, stats, and so on.
org.apache.zookeeper.server.upgrade packages in the ZooKeeper Java APIs are part of the server implementation. The package
org.apache.zookeeper.client defines the class of Four Letter Word, which is used to enquire the state of the ZooKeeper server.
Refer to Chapter 1, A Crash Course in...