public class LangDemo {
  public static void main(String[] args) throws Exception{
      try {
                 //加载驱动
                Class.forName("oracle.jdbc.driver.OracleDriver");
                //创建连接
                Connection   cn=DriverManager.getConnection("jdbc:oracle:thin:@127.0.0.1:1521:XE","hh","hh");
                Statement sm=cn.createStatement();
                //获得结果集
                ResultSet rs=sm.executeQuery("select name,nickname,id from a");
                //遍历结果集
                 while(rs.next()){
System.out.println("name:"+rs.getString(1));//rs.getString(“name”)
System.out.println("nickname:"+rs.getString(2));  //rs.getInt(“id”)                                
}
        } catch (Exception e) {
                   e.printStackTrace();
        }finally{   // rs.close();
                               // conn.close();
                 }
    }
}

public class LangDemo {
  public static void main(String[] args) throws Exception{
    Connection con = null;// 创建一个数据库连接
       PreparedStatement pre = null;// 创建预编译语句对象，一般都是用这个而不用Statement
       ResultSet result = null;// 创建一个结果集对象
     try
      {
        Class.forName("oracle.jdbc.driver.OracleDriver");// 加载Oracle驱动程序
        System.out.println("开始尝试连接数据库！");
        String url = "jdbc:oracle:" + "thin:@127.0.0.1:1521:XE"; // 127.0.0.1是本机地址，XE是精简版Oracle的默认数据库名
        String user ="system";// 用户名,系统默认的账户名
        String password = "147";// 你安装时选设置的密码
        con = DriverManager.getConnection(url, user, password);// 获取连接
        System.out.println("连接成功！");
        String sql = "select * from student where name=?";// 预编译语句，“？”代表参数
        pre = con.prepareStatement(sql);// 实例化预编译语句
        pre.setString(1, "张三");// 设置参数，前面的1表示参数的索引，而不是表中列名的索引
        result = pre.executeQuery();// 执行查询，注意括号中不需要再加参数
        while (result.next())
            // 当结果集不为空时
            System.out.println("学号:" + result.getInt("id") + "姓名:"
                    + result.getString("name"));
     }
      catch (Exception e)
       {
            e.printStackTrace();
        }
       finally  {
            ……..
        } 
    }
}