Central Authentication Service is an enterprise level, open-source, single sign on solution with a Java server component.

List is an ordered collection in java and is used to maintain the sequence of elements in a collection.

Cloning is used to perform shallow or deep copy of java objects. Copy constructor is also used for the same.

Deep Copy And Shallow Copy
Deep Copy And Shallow Copy are two different type copies to copy java objects. Shallow copy just copies reference of the objeect while deep copy copies the content of the object.

equals(), a method in java objects is used to retrieve and compare the objects for equality and if equal a boolean value true will be returned else a boolean value false will be returned.

Externalization is nothing but serialization but by implementing Externalizable interface to persist and restore the object and have the complete control on how to persist the object.

hashCode(), a method in java objects is used to retrieve the objects fast and accurate when objects are compared using equals method.

Inside Set
Set in java is used to have unique collection i.e., the elements in the collection must be unique with cno duplicate elements.

Serialization in java is used to flatten the object and persist the flattened object or send to other JVMs.

serialVersionUID is the version key used by serialization process to identify the object and this will be autogenerated if not provided explicitly.

Static blocks
Static blocks in java are used when a block of code needs to be executed during loading of the class by JVM.