Effective Java

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ITEM 87: CONSIDER USING A CUSTOM SERIALIZED FORM
347
/**
* Middle name, or null if there is none.
* @serial
*/
private final String middleName;
... // Remainder omitted
}
Logically speaking, a name consists of three strings that represent a last name,
a first name, and a middle name. The instance fields in 
Name
precisely mirror this
logical content. 
Even if you decide that the default serialized form is appropriate, you
often must provide a 
readObject
 method to ensure invariants and security.
In
the case of 
Name
, the 
readObject
method must ensure that the fields 
lastName
and 
firstName
are non-null. This issue is discussed at length in Items 88 and 90.
Note that there are documentation comments on the 
lastName
, 
firstName
,
and 
middleName
fields, even though they are private. That is because these private
fields define a public API, which is the serialized form of the class, and this public
API must be documented. The presence of the 
@serial
tag tells Javadoc to place
this documentation on a special page that documents serialized forms.
Near the opposite end of the spectrum from 
Name
, consider the following
class, which represents a list of strings (ignoring for the moment that you would
probably be better off using one of the standard 
List
implementations):