Java ObjectInputStream .registerValidation (ObjectInputValidation obj, int prio)

public void registerValidation(ObjectInputValidation obj,
                                           int prio)
            throws NotActiveException,
                   InvalidObjectException

//from ww  w.  j  a v  a2  s .  c  om

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectInputValidation;
import java.io.ObjectOutputStream;
import java.io.Serializable;

public class Main {

  public static void main(String[] args) throws Exception {
    FileOutputStream out = new FileOutputStream("test.txt");
    ObjectOutputStream oout = new ObjectOutputStream(out);

    oout.writeObject(new Example());
    oout.flush();
    oout.close();
    
    ObjectInputStream ois = new ObjectInputStream(new FileInputStream(
        "test.txt"));


    Example a = (Example) ois.readObject();


    System.out.println(a.s);


    a.validateObject();
    ois.close();
  }

}

class Example implements Serializable, ObjectInputValidation {

  String s = "Hello World from java2s.com!";

  private String readObject(ObjectInputStream in) throws IOException,
      ClassNotFoundException {
      
    ObjectInputStream.GetField gf = in.readFields();

    in.registerValidation(this, 0);


    return (String) gf.get("s", null);
  }

  public void validateObject() throws InvalidObjectException {
    if (this.s.equals("Hello World!")) {
      System.out.println("Validated.");
    } else {
      System.out.println("Not validated.");
    }
  }
}