Worm.java

// serialization/Worm.java
// (c)2021 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.
// Demonstrates object serialization
import java.io.*;
import java.util.*;

class Data implements Serializable {
  private int n;
  Data(int n) { this.n = n; }
  @Override public String toString() {
    return Integer.toString(n);
  }
}

public class Worm implements Serializable {
  private static Random rand = new Random(47);
  private Data[] d = {
    new Data(rand.nextInt(10)),
    new Data(rand.nextInt(10)),
    new Data(rand.nextInt(10))
  };
  private Worm next;
  private char c;
  // Value of i == number of segments
  public Worm(int i, char x) {
    System.out.println("Worm constructor: " + i);
    c = x;
    if(--i > 0)
      next = new Worm(i, (char)(x + 1));
  }
  public Worm() {
    System.out.println("Zero-argument constructor");
  }
  @Override public String toString() {
    StringBuilder result = new StringBuilder(":");
    result.append(c);
    result.append("(");
    for(Data dat : d)
      result.append(dat);
    result.append(")");
    if(next != null)
      result.append(next);
    return result.toString();
  }
  public static void
  main(String[] args) throws ClassNotFoundException,
    IOException {
    Worm w = new Worm(6, 'a');
    System.out.println("w = " + w);
    try(
      ObjectOutputStream out = new ObjectOutputStream(
        new FileOutputStream("worm.dat"))
    ) {
      out.writeObject("Worm storage\n");
      out.writeObject(w);
    }
    try(
      ObjectInputStream in = new ObjectInputStream(
        new FileInputStream("worm.dat"))
    ) {
      String s = (String)in.readObject();
      Worm w2 = (Worm)in.readObject();
      System.out.println(s + "w2 = " + w2);
    }
    try(
      ByteArrayOutputStream bout =
        new ByteArrayOutputStream();
      ObjectOutputStream out2 =
        new ObjectOutputStream(bout)
    ) {
      out2.writeObject("Worm storage\n");
      out2.writeObject(w);
      out2.flush();
      try(
        ObjectInputStream in2 = new ObjectInputStream(
          new ByteArrayInputStream(
            bout.toByteArray()))
      ) {
        String s = (String)in2.readObject();
        Worm w3 = (Worm)in2.readObject();
        System.out.println(s + "w3 = " + w3);
      }
    }
  }
}
/* Output:
Worm constructor: 6
Worm constructor: 5
Worm constructor: 4
Worm constructor: 3
Worm constructor: 2
Worm constructor: 1
w = :a(853):b(119):c(802):d(788):e(199):f(881)
Worm storage
w2 = :a(853):b(119):c(802):d(788):e(199):f(881)
Worm storage
w3 = :a(853):b(119):c(802):d(788):e(199):f(881)
*/