犯罪现场 下载:求救！出现java.lang.NullPointerException问题怎么解决？

2.UserInfo.java
package com;
import java.io.*;
public class UserInfo implements Serializable
{
/**
*
*/
private static final long serialVersionUID = 1L;
private String memb_type;
private String memb_no;
private String memb_pw;
private String link_name;
private String id_no;
private char sex;
private String link_tele;
private String link_fax;
private String link_addr;
private String post_code;
private char vali_sign='0';

//setter方法
public String getMembtype()
{
return this.memb_type;
}
public String getMembno()
{
return this.memb_no;
}
public String getMembpw()
{
return this.memb_pw;
}
public String getLinkname()
{
return this.link_name;
}
public String getId()
{
return this.id_no;
}
public char getSex()
{
return this.sex;
}
public String getTele()
{
return this.link_tele;
}
public String getFax()
{
return this.link_fax;
}
public String getAddr()
{
return this.link_addr;
}
public String getPostcode()
{
return this.post_code;
}
public char getSign()
{
return this.vali_sign;
}

//getter
public void setMembtype(String type)
{
this.memb_type=type;
}
public void setMembno(String no)
{
this.memb_no=no;
}
public void setMembpw(String pw)
{
this.memb_pw=pw;
}
public void setLinkname(String name)
{
this.link_name=name;
}
public void setId(String id)
{
this.id_no=id;
}
public void setSex(char sex)
{
this.sex=sex;
}
public void setTele(String tele)
{
this.link_tele=tele;
}
public void setFax(String fax)
{
this.link_fax=fax;
}
public void setAddr(String addr)
{
this.link_addr=addr;
}
public void setPostcode(String postcode)
{
this.post_code=postcode;
}

}