java接口变量问题

　　　　　　　　　 List<FileItem> items = upload.parseRequest(request);
                Iterator<FileItem> iter = items.iterator();
                while (iter.hasNext()) {
                    FileItem item = iter.next();
                    File file=new File("D:\\b.pdf");
                    if(!file.exists()) 
                    {
                        try {    
                            file.createNewFile();    
                        } catch (IOException e) {    
                            e.printStackTrace();    
                        }    
                    }
                    BufferedOutputStream bos =new BufferedOutputStream(new FileOutputStream(file));
                    BufferedInputStream bfis=new BufferedInputStream(item.getInputStream());
                    byte b[]=new byte[2048];
                    int read=bfis.read(b,0,2048);
                    while(read!=-1)  
                    {  
                        bos.write(b,0,read); 
                        read=bfis.read(b,0,2048);  
                    }  
                    bfis.close();
                    bos.flush();
                    bos.close();

List<FileItem> items = upload.parseRequest(request);

Iterator<FileItem> iter = items.iterator();