First, the toString() method should return a String not an Animals type (or any other type).
Second, you want to override the standard java Object toString() method for your class.
Third, you really want the toString() method in the Animals class instead of AnimalGroup.
Something like:
@Override
public String toString() {
return "Animal: " + name + ", Classification: " + classification;
}
Then in your AnimalGroup printAnimalsList() method change the println call to:
System.out.println(i.toString());
You can get rid of the toString() method in the AnimalGroup class.