Reconstructing an externalizable object

      

// : c12:Blip3.java
// Reconstructing an externalizable object.
// 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;

public class Blip3 implements Externalizable {
  private int i;

  private String s; // No initialization

  public Blip3() {
    System.out.println("Blip3 Constructor");
    // s, i not initialized
  }

  public Blip3(String x, int a) {
    System.out.println("Blip3(String x, int a)");
    s = x;
    i = a;
    // s & i initialized only in nondefault constructor.
  }

  public String toString() {
    return s + i;
  }

  public void writeExternal(ObjectOutput out) throws IOException {
    System.out.println("Blip3.writeExternal");
    // You must do this:
    out.writeObject(s);
    out.writeInt(i);
  }

  public void readExternal(ObjectInput in) throws IOException,
      ClassNotFoundException {
    System.out.println("Blip3.readExternal");
    // You must do this:
    s = (String) in.readObject();
    i = in.readInt();
  }

  public static void main(String[] args) throws IOException,
      ClassNotFoundException {
    System.out.println("Constructing objects:");
    Blip3 b3 = new Blip3("A String ", 47);
    System.out.println(b3);
    ObjectOutputStream o = new ObjectOutputStream(new FileOutputStream(
        "Blip3.out"));
    System.out.println("Saving object:");
    o.writeObject(b3);
    o.close();
    // Now get it back:
    ObjectInputStream in = new ObjectInputStream(new FileInputStream(
        "Blip3.out"));
    System.out.println("Recovering b3:");
    b3 = (Blip3) in.readObject();
    System.out.println(b3);
  }
} ///:~

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Reconstructing an externalizable object : Serialization « File Input Output « Java

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