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());
        }
    }