public boolean retainAll(StructSet ss) { if (!this.structType.equals(ss.structType)) { if (isEmpty()) { return false; // nothing modified } else { clear(); return true; // nothing retained in receiver collection } } boolean changed = false; int size = size(); Iterator it; it = fieldValuesIterator(); while (size-- > 0) { Object[] vals = (Object[]) it.next(); if (!ss.containsFieldValues(vals)) { it.remove(); changed = true; } } return changed; }