java.lang.Object | +--java.io.Serializable | +--java.io.ExternalizableAll Implemented Interfaces:
void | readExternal(java.io.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(java.io.ObjectOutput out) This method is responsible for writing the instance data of an object to the passed in stream. |
public void readExternal(java.io.ObjectInput in)
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
in
- An ObjectInput
instance for reading in the object stateClassNotFoundException
- If the class of an object being restored cannot be foundIOException
- If any other error occurspublic void writeExternal(java.io.ObjectOutput out)
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
.
out
- An ObjectOutput
instance for writing the object stateIOException
- If an error occurs
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 thereadExternal
method is used to restore the state.