public void clear(){
synchronized (lock) {
    items.clear();
  }
  itemPositionChangeChecked=new SparseBooleanArray(items.size());
  notifyDataSetChanged();
}

public void clear ( ) { synchronized ( lock ) { items . clear ( ) ; } itemPositionChangeChecked = new SparseBooleanArray ( items . size ( ) ) ; notifyDataSetChanged ( ) ; }
remove all elements from the list .
