Коллекция классов

import java.io.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
 
/**
 * Created by IntelliJ IDEA.
 * User: rtimoshenko
 * Date: 13.12.2011
 * Time: 14:26:07
 * To change this template use File | Settings | File Templates.
 */
 
enum AgeGroup {
    AGEUNLIMITED,
    AGE2TO3,
    AGE3TO5,
    AGE6TO9
}
 
interface Toy extends Serializable {
    String getToyName();
    String getName();
    int getPrice();
    AgeGroup getAge();
}
 
abstract class SomeToy implements Toy {
    private int price = 0;
    private AgeGroup ageGroup = AgeGroup.AGEUNLIMITED;
    private String name = "";
    public SomeToy() {}
    public SomeToy(String name, int price, AgeGroup ageGroup) {
        this.name = name;
        this.price = price;
        this.ageGroup = ageGroup;
    }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public int getPrice() { return price; }
    public void setPrice(int price) { this.price = price; }
    public AgeGroup getAge() { return ageGroup; }
    public void setAge(AgeGroup ageGroup) { this.ageGroup = ageGroup; }
    public String toString() {
        return "The " + getToyName() + " " + getName() + " for " + getAge() + " costs " + getPrice() / 100.;
    }
}
 
class Doll extends SomeToy {
    private int size = 0;
    Doll() { super(); }
    Doll(String name, int price, AgeGroup ageGroup, int size) {
        super(name, price, ageGroup);
        this.size = size;
    }
    public int getSize() { return size; }
    public void setSize(int size) { this.size = size; }
    public String getToyName() { return "doll"; }
    public String toString() {
        return super.toString() + ", size: " + getSize() + "cm";
    }
}
 
class Ball extends SomeToy {
    private int weight = 0;
    Ball() { super(); }
    Ball(String name, int price, AgeGroup ageGroup, int size) {
        super(name, price, ageGroup);
        this.weight = size;
    }
    public int getWeight() { return weight; }
    public void setWeight(int size) { this.weight = size; }
    public String getToyName() { return "ball"; }
    public String toString() {
        return super.toString() + ", weight: " + getWeight() + "g";
    }    
}
 
 
public class Launcher {
    public static void save(String fileName, Collection<Toy> toys) throws FileNotFoundException, IOException {
        ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(fileName));
        for (Toy toy : toys)
            out.writeObject(toy);
        out.close();
    }
    public static Collection<Toy> load(String fileName) throws IOException, ClassNotFoundException {
        ObjectInputStream in = new ObjectInputStream(new FileInputStream(fileName));
        Collection<Toy> result = new ArrayList<Toy>();
        try {
            while (true) {
                Toy value = (Toy)in.readObject();
                result.add(value);
            }
        } catch (EOFException e) {}
        in.close();
        return result;
    }
    public static void main(String... args) throws IOException, ClassNotFoundException {
        Collection<Toy> toys = new ArrayList<Toy>(Arrays.asList(
            new Doll("Masha", 1222, AgeGroup.AGE3TO5, 12),
            new Ball("Basketball ball", 1403, AgeGroup.AGEUNLIMITED, 300)
        ));
        save("temp", toys);
        System.out.println(load("temp"));
    }
}