class Some
{
    ArrayList<EmptyPresent> emptyPresents;

    // Object initialiser
    {
        emptyPresents = new ArrayList<EmptyPresent>();
    }
}

vs.

class Some
{
    void someMethod()
    {
        ArrayList<EmptyPresent> emptyPresents;

        {
            emptyPresents = new ArrayList<EmptyPresent>();
        }
    }
}