java.io
public interface Externalizable extends Serializable
Note that classes which implement this interface must take into account that all superclass data must also be written to the stream as well. The class implementing this interface must figure out how to make that happen.
This interface can be used to provide object persistence. When an
object is to be stored externally, the writeExternal method is
called to save state. When the object is restored, an instance is
created using the default no-argument constructor and the
readExternal method is used to restore the state.
| Method Summary | |
|---|---|
| void | readExternal(ObjectInput in)
This method restores an object's state by reading in the instance data
for the object from the passed in stream. |
| void | writeExternal(ObjectOutput out)
This method is responsible for writing the instance data of an object
to the passed in stream. |
InputStream, but rather is a class that
implements
the ObjectInput interface. That interface provides a
mechanism for
reading in Java data types from a stream.
Note that this method must be compatible with writeExternal.
It must read back the exact same types that were written by that
method in the exact order they were written.
If this method needs to read back an object instance, then the class
for that object must be found and loaded. If that operation fails,
then this method throws a ClassNotFoundException
Parameters: in An ObjectInput instance for reading in the object
state
Throws: ClassNotFoundException If the class of an object being restored cannot be found IOException If any other error occurs
OutputStream, but rather is a class that implements the
ObjectOutput interface. That interface provides a
number of methods
for writing Java data values to a stream.
Not that the implementation of this method must be coordinated with
the implementation of readExternal.
Parameters: out An ObjectOutput instance for writing the
object state
Throws: IOException If an error occurs