JavaでOracleデータベースとJDBCを接続する方法の紹介（コード付き）

import java.sql.Connection;
import java.sql.SQLException;
import java.sql.DriverManager;
import java.sql.ResultSet;
//import java.sql.Statement;
import java.sql.PreparedStatement;
public class Jdbcconnect {   public static void main(String[] args) {   
final String URL = "jdbc:oracle:thin:@ip/实例名";  
final String USER = "数据库用户名";   
final String PWD = "密码";
  try {  
  //加载驱动程序    Class.forName("oracle.jdbc.OracleDriver");   
 System.out.println("加载驱动成功！");  
 }catch (Exception  e){    System.out.println("加载驱动异常"+e);  
 }   try {    //获得数据库连接   
 Connection con = DriverManager.getConnection(URL,USER,PWD);    
System.out.println("加载数据库连接成功！");
   String sql = "select * from t_sys_user";
   PreparedStatement pt  = con.prepareStatement(sql);    
ResultSet rs = pt.executeQuery();   
 System.out.println(rs.next());   
 while(rs.next()) {    
 String userid = rs.getString("userid");    
 System.out.println(userid);    }   
 rs.close();    pt.close();    
con.close();
      }catch (SQLException e){    System.out.println("加载数据库连接异常"+e);   }     }  
}