Does a class with has-a relationship with a Collection object have a relationship with the Collection's elements?

Question

I am studying for the Java 8 Programmer II certification, and I'm going over the relationships classes can have. I understand composition, but I wondered if there is relationship considered between the elements of a collection that is a class variable of a class and that class. For instance, consider this code:

public class A {
    static ArrayList<String> strings = new ArrayList<String>();

    public A() {
        strings.add("foo");
    }
}

Do we say that the String elements of strings have a relationship with class A?

Answer 1

First of all we should make clear if classes A and String would be in relationship if class A would have simple String field like so:

public class A {
    static String aString;

    public A() {
       aString = "foo";
    }
}

... I think so! And that would be "has-a" realtionship - A has-a String.

In your example there's a collection of Strings. We can also say that class A has-a (lot of ;) Strings... You can imagine that class A has a lot of relationships with String objects; class A aggregates them in collection. This is analogous to well known composition example "car 'has' wheels".

You can also say that this is unidirectional one-to-many relationship (unidirectional because only one side of this relationship knows about the other).