简单的更改记录的语句?

JAVABEAN功能:添加一条新记录.并按新记录的style(分类)把stylelist表中相同style(分类)的cou加1.
分不多了.谢谢各位帮帮忙!/*
 *网站JAVABEAN
 *添加一条新信息,
 *添加成功显示提示及继续添加的链接.
 *前台页面
 */
package mybean;import java.sql.*;public class Publish {
    
private PreparedStatement pstmt = null;
private Statement stmt = null;
         private Connection conn = null;
private String city;
private String title;
private String style;
private String content;
private String pass;
private String chec;
private String addMessage;

public Publish(){}
    
public void setCity(String city){
this.city=city;
}
public void setTitle(String title){
     this.title=title;   
    }
    public void setStyle(String style){
     this.style=style;
    }
    public void setContent(String content){
     //替换HTML字符输出的格式
     content=content.replace("\n","<BR/>");
     content=content.replace(" ","&nbsp;");
     this.content=content;
    }
    public void setPass(String pass){
     this.pass=pass;
    }
    public void setChec(String chec){
     this.chec=chec;
    }
    
    public String getCity(){
     return this.city;
    }
    public String getTitle(){
     return this.title;
    }
    public String getStyle(){
     return this.style;
    }
    public String getContent(){
     return this.content;
    }
    public String getPass(){
     return this.pass;
    }
    public String getChec(){
     return this.chec;
    }
public String getAddMessage(){
conn = DBConnSource.getConnection("jdbc/myweb");
         
    try{ 
     String sql="INSERT INTO adver VALUES(?,?,?,?,?,?,?,?)";   
    pstmt = DBConnSource.getPstmt(conn,sql);
java.util.Date date=new java.util.Date();
Timestamp tt=new Timestamp(date.getTime());
pstmt.setInt(1,0);
pstmt.setString(2,city);
pstmt.setString(3,style);
pstmt.setString(4,title);
pstmt.setString(5,content);
pstmt.setTimestamp(6,tt);
pstmt.setString(7,pass);
pstmt.setString(8,chec);

int flag=pstmt.executeUpdate();
if(flag>0){
addMessage="成功添加"+flag+"条记录!";
String sql2="UPDATE stylelist SET cou=cou+1 WHERE style='"+style+"'";
                stmt.executeUpdate(sql2); //这一句是Publish.java:89
    }else{
    addMessage="添加记录失败";
    }
   }catch(SQLException e) {
        e.printStackTrace();
    }finally{
     DBConnSource.close(stmt);
        DBConnSource.close(pstmt);
        DBConnSource.close(conn);
    }               
 return addMessage;
}
}报错:
exception org.apache.jasper.JasperException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:510)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause java.lang.NullPointerException
mybean.Publish.getAddMessage(Publish.java:89)
org.apache.jsp.publish2_jsp._jspService(publish2_jsp.java:139)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)