如何使用JDBC将数据更新到数据库

            Class.forName("oracle.jdbc.driver.OracleDriver");
            Connection con = 
           DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe", 
           "system", "9900479852");
            Statement stmt =con.createStatement();
            ResultSet rs = stmt.executeQuery("select *from registration where emailid='"+str+"' ");

             // here im fetching the emailid from data base
             while(rs.next()){

             emailId = rs.getString("emailId");
             mob = rs.getString("mobilenumber");
             System.out.println(emailId);

             //here we return update query`enter code here`
             if(emailId.equals(str)){
             stmt.executeQuery("update registration set password='"+s1+"' 
             where emailId='"+str+" '"); //query is executing but new vales are not updating to the data base
             p.println("updated");
             }
             con.close();    
             }
            Class.forName("oracle.jdbc.driver.O