Hi friend...


Externalizable interface :

When user use Serializable interface, class is serialized by default but Externalizable interface
provides facility to complete control over serialization process so Externalization is a more advanced
alternative to serialization.
This interface has two methods:
1:- public void writeExternal(ObjectOutput out)
2:- public void readExternal(ObjectInput in)

Every class that usese/implements externalization must implement Externalizable interface and override these methods
and must have a no arguments constructor. These methods are automatically called at the time of serialization
and de-serialization so you can can implement your own serialization-specific operations and have control over what data
to serialize and wat to not.

Example Code :


import java.io.*;

public class MyExternObject implements Externalizable {

int i;
String s;

MyExternObject() {
i = 256;
s = new String("Implementation of interface Externalizable.");
}

public int getI() {
return i;
}

public String getS() {
return s;
}

public void writeExternal(ObjectOutput out) throws
IOException {
out.writeInt(this.i);
out.writeObject(this.s);
}

public void readExternal(ObjectInput in) throws
IOException, ClassNotFoundException {
this.i = in.readInt();
this.s = (String) in.readObject();
}

public static void main(String[] args) throws
IOException, ClassNotFoundException {

MyExternObject externObject = new MyExternObject();
System.out.println(externObject.getS());
System.out.println(externObject.getI());
}
}

Output :
Implementation of interface Externalizable.
256


Thanks..

Read for more information,


http://www.roseindia.net/java/