'Something wrong' is not helpful.  What is wrong?  Quote a stack traces or
compiler errors.

However try this to begin with

// create new Volunteer
Volunteer volunteer = new Volunteer(String name, int telephone);

// Call add method with new volunteer
add(volunteer);

// add method
public boolean add(Volunteer volunteer)
   {
       Iterator it = volunteers.iterator();
           while (it.hasNext())
       {
           Volunteers volunteers = (Volunteers) it.next();
               if (volunteers.getName().equals(volunteer.getName())) //
does existing collection contain volunteer?
                   return false; // false indictating can't add
      }
       volunteers.add(volunteer); // no volunteer of this name, so add
       return true; // return true indicating success
   }
}

You'll need a getName() method in your Voluteer class which I imagine you
have or should have.

--
Mike W

What is this supposed to be?
If a method declaration, you can't have a dot in a method name.
If this is supposed to be an anonymous class, then you don't want the
word public there.

Iterators are more neatly handled with for:each.

The contains method might do what you want if your volunteers supports
it.

In article
<73094ec574c1a58aebddecfff73e2086@localhost.talkaboutprogramming.com>,

You have an assignment over XMas break?

One problem is that you either have two classes with nearly the same
name (Volunteer, Volunteers), or else you've confused the two of them.
If you can't figure this out from the error code -- which you didn't
post, then you need to go to your professor's office hours.

mehaase(at)gmail(dot)com