public boolean add(Object element) 
{
        return getDoubleCollection().add(((Number)element).doubleValue());
}

 public boolean addAll(Collection c) 
{
        return getDoubleCollection().addAll(CollectionDoubleCollection.wrap(c));
}

 public  void clear() 
{
        getDoubleCollection().clear();
}

 public boolean contains(Object element) 
{
        return getDoubleCollection().contains(((Number)element).doubleValue());
}

 public boolean containsAll(Collection c) 
{
        return getDoubleCollection().containsAll(CollectionDoubleCollection.wrap(c));
}

 abstract protected DoubleCollection getDoubleCollection()

 public boolean isEmpty() 
{
        return getDoubleCollection().isEmpty();
}

 public Iterator iterator() 
{
        return DoubleIteratorIterator.wrap(getDoubleCollection().iterator());
}

wraps the DoubleIterator returned by my underlying DoubleCollection , if any.

 public boolean remove(Object element) 
{
        return getDoubleCollection().removeElement(((Number)element).doubleValue());
}

 public boolean removeAll(Collection c) 
{
        return getDoubleCollection().removeAll(CollectionDoubleCollection.wrap(c));
}

 public boolean retainAll(Collection c) 
{
        return getDoubleCollection().retainAll(CollectionDoubleCollection.wrap(c));
}

 public int size() 
{
        return getDoubleCollection().size();
}

 public Object[] toArray() 
{
        double[] a = getDoubleCollection().toArray();
        Object[] A = new Object[a.length];
        for(int i=0;i< a.length;i++) {
            A[i] = new Double(a[i]);
        }
        return A;
}

 public Object[] toArray(Object[] A) 
{
        double[] a = getDoubleCollection().toArray();
        if(A.length <  a.length) {
            A = (Object[])(Array.newInstance(A.getClass().getComponentType(), a.length));
        }
        for(int i=0;i< a.length;i++) {
            A[i] = new Double(a[i]);
        }
        if(A.length  > a.length) {
            A[a.length] = null;
        }
        return A;
}

 public String toString() 
{
        return getDoubleCollection().toString();
}