OK.
Togawa kakwo prechi da imash Map ot (String, Object), kydeto String e imeto na dejnostta (Activity), a Object e class-a, kojto implement-wa taja dejnost. I da tyrsish wytre po ime.

class Company {
private final Map activities = new HashMap();

void addActivity(Activity activity) {
this.activities.put(activity.getName(), activity);
}

void removeActivity(String activityName){
this.activities.remove(activityName);
}

void is(String activityName) {
return this.activities.containsKey(activityName);
}

Object as(String activityName) {
return this.activities.get(activityName);
}
}

abstract class Activity {
private final String name;

protected Activity(String name) {
this.name = name;
}

String getName() {
return this.name;
}
}

class Seller extends Activity {
Seller() {
super("seller");
}

int getGoodsSelled() {
// bla, bla, bla
}
}

class Transporter extends Activity {
Transporter() {
super("transporter");
}

int getCarsAvailable() {
// bla, bla, bla
}
}

void test(Company c) {
if (!c.is("seller")) {
System.out.println("not a seller");
}
Seller seller = (Seller) c.as("seller");
System.out.println("Goods selled: " + seller.getGoodsSelled());

if (!c.is("transporter")) {
System.out.println("not a transporter");
}
Transported transporter = (Transporter) c.as("transporter");
System.out.println("Cars available: " + transported.getCarsAvailable());
}


Ami towa e, koeto mi hrumwa. Trjabwa da widish kak shte gi map-nesh kym DB.