private boolean savebill(String saveFile){
         boolean return_val = true;
         String unknownComsumer = "......................";
         if(No_cu.getText().isEmpty()){
             No_cu.setText("0.0");
         }
         try{
             Double.parseDouble(No_cu.getText());
         }catch(NumberFormatException e){
             show_message("Lỗi, Coi lại số nợ");
             return_val = false;
         }
         if(return_val){
            try{
               FileOutputStream fos = new FileOutputStream(saveFile);
               Writer out = new OutputStreamWriter(fos, "UTF8");
               {
                   int paid_count = Paid_MaSP.size();
                   if(ten_khach_hang.getText().trim().isEmpty()){
                       ten_khach_hang.setText(unknownComsumer);
                   }
                   out.write("==+"+ ten_khach_hang.getText() + "\n");
                   for(int i = 0; i < paid_count; i++)
                   {
                       out.write("===" + Paid_MaSP.get(i) + "<>"
                               + Paid_TenSP.get(i) + "<>"
                               + Paid_GiaSSP.get(i) + "<>"
                               + Paid_GiaLSP.get(i) + "<>"
                               + Paid_SoLuongSP.get(i) + "<>"
                               + Paid_TongGiaSP.get(i) + "\n");
                   }
                   out.write("==-"+ No_cu.getText() + "\n");
                   out.close();
               }
            }catch (Exception e){//Catch exception if any
                thongbao_text("[Lỗi] Không mở được file" + saveFile, Color.RED);
                return_val = false;
            }
         }
         return return_val;
     }