Also available as SerializePlay.java

/**
 * Title: SerializePlay
 * Description: Using Serializable interface and ObjectStreams
 * @author hollingd@cs.rpi.edu
 */

import java.io.*;

// a base class that includes a couple of fields

abstract class Base {
        int x;
        String name;

        Base() {
                x=0;
                name="noname";
        }

        Base(int i, String s) {
                x=i;
                name=s;
        }
}


// a derived class that adds a new field and is serializable

class Foo extends Base implements Serializable{

        String fooString;

        Foo() {
                super();
                fooString="nofoostring";
        }

        Foo( int x, String n, String f) {
                super(x,n);
                fooString=f;
        }

        public String toString() {
                return "Foo:\n\tx: " + x + "\n\t" +
                        "Name: " + name + "\n\t" +
                        "FooString: " + fooString + "\n";
        }
}


// a main and a couple of methods for playing with 
// serializeable objects. 
public class SerializePlay {

        static public void main(String []args)
             throws IOException,ClassNotFoundException{
                 // probably want to comment out one of these for testing
                 write();
                 // read();
        }

        // write() generates a list of 5 Foo objects and then writes
        // them to the file named "save" (as Objects)

        static public void write() throws IOException,ClassNotFoundException{
                Foo[] f = new Foo[5];

                for (int i=0;i<5;i++) {
                        f[i] = new Foo(i,"my name is " + Integer.toString(i), "Foo # " + i);
                }

                for (int i=0;i<5;i++) {
                        System.out.println(f[i]);
                }

                // create an ObjectOutputStream associated with the file "save"
                ObjectOutputStream dos = new ObjectOutputStream(
                                                                                                        new FileOutputStream("save"));
                // write each Foo object to the file
                for (int i=0;i<5;i++) {
                        dos.writeObject(f[i]);
                }
                dos.close();
                System.out.println("Done");
        }


        // read() reads 5 Foo objects from the file "save"
        // and prints them out.

        static public void read() throws IOException,ClassNotFoundException{
                ObjectInputStream ois = new ObjectInputStream(
                                                          new FileInputStream("save"));

                Foo[] blah = new Foo[5];

                int i=0;
                boolean done=false;

                // Use EOFException to control when the loop ends

                while (! done) {
                        try {
                                blah[i] = (Foo) ois.readObject();
                                System.out.println("Read one foo");
                                i++;
                        } catch( EOFException e) {
                                done=true;
                        }
                } 
                // print out the 5 we got.
                for ( i=0;i<5;i++) {
                        System.out.println(blah[i]);
                }

        }
}