我的这些代码是错的，实现不了？该怎么改？各位大神帮帮忙，纠结好几天了！
List cartlist2=(List)session.getAttribute("cartlist2");
List list=new ArrayList();
for(int i=0;i<cartlist.size();i++){
goods=(Goods)cartlist.get(i);
for(int j=0;j<cartlist2.size();j++){
goods2=(Goods)cartlist2.get(j);
if(goods.getGid().equals(goods2.getGid())){
int gnumber=goods2.getGnumber();
goods2.setGnumber(gnumber+1);
list.add(goods2);
cartlist2.remove(goods2);
break;
}else{
String gid=goods.getGid();
String gname=goods.getGname();
int gprice=goods.getGprice();
String gpress=goods.getGpress();
int gpostage=goods.getGpostage();
int gnumber=1;
goods3=new Goods(gid,gname,gprice,gpress,gpostage,gnumber);
list.add(goods3);
}
}
}
for(int k=0;k<list.size();k++){
goods3=(Goods)list.get(k);
cartlist2.add(goods3);
}
session.setAttribute("cartlist2",cartlist2);
//response.sendRedirect("shoppingcart.jsp");
request.getRequestDispatcher("shoppingcart.jsp").forward(request, response);
