If you are trying use Composite pattern, looks like this.
http://en.wikipedia.org/wiki/Composite_pattern
interface Animal{
void sound();
}
class CompositeAnimal implements Animal {
List<Animal> animals;
@Override
public void sound() {
for (Animal animal : animals) {
animal.sound();
}
}
}
class Dog implements Animal {
...
}
class Cat implements Animal {
...
}