In java create a class file with hashmap at runtime

We can save and retrieve the java objects into file at run time.

Saving object should implement Serializable interface

class Person implements Serializable{

String firstName;
String lastName;

public Person(String firstName, String lastName) {
    super();
    this.firstName = firstName;
    this.lastName = lastName;
}
public String getFirstName() {
    return firstName;
}
public void setFirstName(String firstName) {
    this.firstName = firstName;
}
public String getLastName() {
    return lastName;
}
public void setLastName(String lastName) {
    this.lastName = lastName;
}
@Override
public String toString() {
    return "Person [firstName=" + firstName + ", lastName=" + lastName
            + "]";
}   

}

public class HashMapSerialization {

public static void main(String[] args) throws Exception {

     Map<String, Person> map = new HashMap<String, Person>();
        map.put("1", new Person("firstName1","lastName1"));
        map.put("2", new Person("firstName2","lastName2"));
        map.put("3", new Person("firstName3","lastName3"));
        FileOutputStream fos = new FileOutputStream("person.ser");
        ObjectOutputStream oos = new ObjectOutputStream(fos);
        oos.writeObject(map);
        oos.close();   
}

}

public class HashMapDeSerialization {

public static void main(String[] args) throws Exception {
     FileInputStream fis = new FileInputStream("person.ser");
        ObjectInputStream ois = new ObjectInputStream(fis);
        Map<String, Person> anotherMap = (Map) ois.readObject();
        ois.close();
        Set keySet = anotherMap.keySet();
        for (Object object : keySet) {
            Person person = anotherMap.get((String)(object));
            System.out.println(person.toString());
        }
}

}