看一下，为什么我的这个jdbc不能连接DB2数据库！

package com.top.comm;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class Dbconn {
 Connection conn=null;
 
 String url="jdbc:db2://127.0.0.1:50000/customer";
 String user="db2admin";
 String password="123456";
 
 public Connection con(){
  try {
   Class.forName("COM.ibm.db2.jdbc.app.DB2Driver").newInstance();
   try {
    conn=DriverManager.getConnection(url,user,password);
   } catch (SQLException e) {
    e.printStackTrace();
   }
  } catch (InstantiationException e) {
   e.printStackTrace();
  } catch (IllegalAccessException e) {
   e.printStackTrace();
  } catch (ClassNotFoundException e) {
   e.printStackTrace();
  }
  return conn;
 }
 public void closecon(){
  if(conn!=null)
   try {
    conn.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
 }
 public static void main(String args[]){
  Dbconn dbc=new Dbconn();
  
  System.out.println(dbc.con());
 }

}

输不出来连接地址！

下面是抛出的异常：

java.sql.SQLException: No suitable driver found for jdbc:db2://127.0.0.1:50000/customer
null
 at java.sql.DriverManager.getConnection(DriverManager.java:602)
 at java.sql.DriverManager.getConnection(DriverManager.java:185)
 at com.top.comm.Dbconn.con(Dbconn.java:18)
 at com.top.comm.Dbconn.main(Dbconn.java:42)