java jdbc SQL 遇到的坑！

java 使用jdbc调用MYSQL 遇到一个诡异的坑，同样的插入语句，总是报语法错误。上代码：

            String insertSQL = "insert into " + tablename + "(date, paraname, paravalue) values(?, ?, ?)";
            PreparedStatement pstm = conn.prepareStatement(insertSQL);
            int rand = 1000000000 + new Random().nextInt(1000000000);
            java.sql.Date adate = new java.sql.Date(System.currentTimeMillis() - rand);
            pstm.setDate(1, adate);
            pstm.setString(2, points.get(0));
            pstm.setFloat(3, 1.0F);
            pstm.execute(insertSQL);

每次都报告语法错误：

check the manual that corresponds to your MySQL server version for the right syntax to use near '?, ?, ?)' at line 1

几经查找，最后才发现，调用格式错误！！应该直接调用execute()；不带参数！！！耗费了半天的时间，冤啊！！

所以，记录在案！