求大佬帮忙，为啥null没有改成0，或者该这么改

 String count =
                "SELECT * FROM  wx_user";
        PreparedStatement ptc = con.prepareStatement(count);
        ResultSet rsc = ptc.executeQuery();
        while (rsc.next()){
            String t_count = String.valueOf(rsc.getInt("t_count"));
            String callid = rsc.getString("callid");
            String called = rsc.getString("called");
            if (t_count == null){
                String count1 =
                        "UPDATE wx_user SET t_count = ? WHERE callid = ? AND called = ?";
                PreparedStatement ptc1 = con.prepareStatement(count1);
                ptc1.setInt(1,0);
                ptc1.setString(2,callid);
                ptc1.setString(3,called);
                ptc1.executeUpdate();
            }

null 咋换成0呢

看起来代码为什么问题，建议你打印出SQL，去数据库执行一下看看，应该是你的查询条件没有查询出记录，所以无法更新