// serialization/Blips.java

// (c)2017 MindView LLC: see Copyright.txt

// We make no guarantees that this code is fit for any purpose.

// Visit http://OnJava8.com for more book information.

// Simple use of Externalizable & a pitfall

import java.io.*;

class Blip1 implements Externalizable {

public Blip1() {

System.out.println("Blip1 Constructor");

}

@Override

public void writeExternal(ObjectOutput out)

throws IOException {

System.out.println("Blip1.writeExternal");

}

@Override

public void readExternal(ObjectInput in)

throws IOException, ClassNotFoundException {

System.out.println("Blip1.readExternal");

}

}

class Blip2 implements Externalizable {

Blip2() {

System.out.println("Blip2 Constructor");

}

@Override

public void writeExternal(ObjectOutput out)

throws IOException {

System.out.println("Blip2.writeExternal");

}

@Override

public void readExternal(ObjectInput in)

throws IOException, ClassNotFoundException {

System.out.println("Blip2.readExternal");

}

}

public class Blips {

public static void main(String[] args) {

System.out.println("Constructing objects:");

Blip1 b1 = new Blip1();

Blip2 b2 = new Blip2();

try(

ObjectOutputStream o = new ObjectOutputStream(

new FileOutputStream("Blips.serialized"))

) {

System.out.println("Saving objects:");

o.writeObject(b1);

o.writeObject(b2);

} catch(IOException e) {

throw new RuntimeException(e);

}

// Now get them back:

System.out.println("Recovering b1:");

try(

ObjectInputStream in = new ObjectInputStream(

new FileInputStream("Blips.serialized"))

) {

b1 = (Blip1)in.readObject();

} catch(IOException | ClassNotFoundException e) {

throw new RuntimeException(e);

}

// OOPS! Throws an exception:

//- System.out.println("Recovering b2:");

//- b2 = (Blip2)in.readObject();

}

}

/* Output:

Constructing objects:

Blip1 Constructor

Blip2 Constructor

Saving objects:

Blip1.writeExternal

Blip2.writeExternal

Recovering b1:

Blip1 Constructor

Blip1.readExternal

*/