if (context.get() == null) return null; LinkedList ll = (LinkedList) context.get(); if (index < 0 || index >= ll.size()) return null; return ll.get(ll.size() - index - 1);
if (index < 0 || index >= _context.size()) return null; return _context.get(_context.size() - index - 1);
    public Object previousContext(int index)    {        if (context.get() == null) return null;        LinkedList ll = (LinkedList) context.get();        if (index < 0 || index >= ll.size()) return null;        return ll.get(ll.size() - index - 1);    }