随机数

 public  void guan() {        for (int i = 0; i <list.size() ; i++) {            Random random = new Random();            //生成list。size的随机书            int i1 = random.nextInt(list.size());            Picasso.with(this).load(list.get(i1).getPic()).into(im);            tv.setText(list.get(i1).getTitle());        }    }