Mega Code Archive
Simple use of Externalizable and a pitfall
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// : c12:Blips.java
// Simple use of Externalizable & a pitfall.
// {Clean: Blips.out}
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
import java.io.Externalizable;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;
class Blip1 implements Externalizable {
public Blip1() {
System.out.println("Blip1 Constructor");
}
public void writeExternal(ObjectOutput out) throws IOException {
System.out.println("Blip1.writeExternal");
}
public void readExternal(ObjectInput in) throws IOException,
ClassNotFoundException {
System.out.println("Blip1.readExternal");
}
}
class Blip2 implements Externalizable {
Blip2() {
System.out.println("Blip2 Constructor");
}
public void writeExternal(ObjectOutput out) throws IOException {
System.out.println("Blip2.writeExternal");
}
public void readExternal(ObjectInput in) throws IOException,
ClassNotFoundException {
System.out.println("Blip2.readExternal");
}
}
public class Blips {
// Throw exceptions to console:
public static void main(String[] args) throws IOException,
ClassNotFoundException {
System.out.println("Constructing objects:");
Blip1 b1 = new Blip1();
Blip2 b2 = new Blip2();
ObjectOutputStream o = new ObjectOutputStream(new FileOutputStream(
"Blips.out"));
System.out.println("Saving objects:");
o.writeObject(b1);
o.writeObject(b2);
o.close();
// Now get them back:
ObjectInputStream in = new ObjectInputStream(new FileInputStream(
"Blips.out"));
System.out.println("Recovering b1:");
b1 = (Blip1) in.readObject();
// OOPS! Throws an exception:
//! System.out.println("Recovering b2:");
//! b2 = (Blip2)in.readObject();
}
} ///:~
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