Java™ How To Program (Early Objects), Tenth Edition

15.5 Object Serialization

In Section 15.4, we demonstrated how to write the individual fields of a record into a file as text, and how to read those fields from a file. When the data was output to disk, certain information was lost, such as the type of each value. For instance, if the value "3" is read from a file, there’s no way to tell whether it came from an int, a String or a double. We have only data, not type information, on a disk.

Sometimes we want to read an object from or write an object to a file or over a network connection. Java provides object serialization for this purposes. A serialized object is an object represented as a sequence of bytes that includes the object’s data as well as information about the object’s type and the ...