java mysql 简单操作

package javatest;
import java.sql.*; 
public class DBconn
{
    // 驱动程序名
  final  String driver = "com.mysql.jdbc.Driver"; 

    // URL指向要访问的数据库名test
  final  String url = "jdbc:mysql://127.0.0.1:3306/udp";

    // MySQL配置时的用户名
  final  String user = "root";

    // MySQL配置时的密码
  final    String password = "root"; 
	public    Connection conn =null;
	public   Statement statement=null;
    public  DBconn()
    {
	    try { 
	     // 加载驱动程序
	     Class.forName(driver); 	
	     // 连续数据库
	     conn = DriverManager.getConnection(url, user, password); 
	     statement = conn.createStatement();	   
	    // if(!conn.isClosed()) 
	     // System.out.println("Succeeded connecting to the Database!"); 
	    } catch(Exception e) { 
	    }
		
	  
    }

    
    public void DBcolse()
    {
    	try
    	{ 
    		
    		this.conn.close(); 

    	} catch(Exception e)
    	{  
		     e.printStackTrace();  
		     System.out.println("数据库关闭失败!"); 
    	} 

    }


}

 DBconn db1=new DBconn();
			 ResultSet rs =null;
			 try{	
				 System.out.println("用户请求注册");		 
				out.println("please input name");	
			 user_name =in.readLine().trim();
			 out.println("please input password");	
			 user_password =in.readLine().trim();
			 }catch (Exception e) 
			 { 
				 System.out.println(e);
			 }			
			 try
			 {
				 String sql= "select * from user where name='"+user_name+"'";
				
				 rs = db1.statement.executeQuery(sql); 
				 
				if(rs.next())
				{
					System.out.println(user_name+"已经注册"); 	
					out.println(user_name+"已经注册");
					
				}
				else
				{
				String sql_insert= "insert into user(name,password) values( '"+ user_name+"' , '"+user_password+"' )";
				System.out.println( db1.statement.executeUpdate(sql_insert));
				System.out.println("注册成功,成功添加了"+user_name+user_password);
				out.println("注册成功,成功添加了"+user_name+user_password);
				}
					 
			}
			 catch (Exception e) 
			 { 
				 System.out.println(e);
			 }	

更新数据 

 String sql= "update unit set "+field_id+" ='"+value+"' where device_id="+device_id+" and index_in_device="+unit_id+"";
      out.println(sql);
     
      DBconn db1=new DBconn();
      int rs;
    
     rs = db1.statement.executeUpdate(sql);   
     System.out.println("updata number="+rs);