为什么我不能连接JSON？

我需要连接BasicDBList中的所有BasicDBObject。每次循环运行时，我的BasicDBObject只包含ONE json元素，并退出我的BasicDBList不包含任何内容。
为什么会发生这种情况？将dbLinha.clear()放在避免重复但每次循环运行时评估代码BasicDBList包含重复！为什么我不能连接JSON？

public BasicDBList readMetadados(Planilha planilha) { 
     List<String> cabecalho = new ArrayList<>(); 
     int linhaReferencia = 0; 
     BasicDBObject dbLinha = new BasicDBObject(); 
     BasicDBList listLinha = new BasicDBList(); 

     try { 
      InputStream planilhaFile = new FileInputStream(FileUtils.getFile(UPLOAD_PATH, planilha.getPath())); 
      Sheet linhaInicial = new XSSFWorkbook(planilhaFile).getSheetAt(0); 
      Iterator<Row> rowIterator = linhaInicial.iterator(); 

      while (rowIterator.hasNext()) { 
       Row row = rowIterator.next(); 
       Iterator<Cell> cellIterator = row.cellIterator(); 
       while (cellIterator.hasNext()) { 
        Cell cell = cellIterator.next(); 
        try { 
         if (cell.getCellType() != 3) { 

          if (cell.getCellType() == 1) { 
           if ("Veículo".equals(cell.getStringCellValue())) { 
            linhaReferencia = cell.getRow().getRowNum(); 
            cabecalho.add(cell.getStringCellValue()); 
            while (cellIterator.hasNext()) { 
             cabecalho.add(cellIterator.next().getStringCellValue()); 
            } 
            break; 
           } 
          } 

          if (linhaReferencia != 0) { 
           switch (cell.getCellType()) { 
            case Cell.CELL_TYPE_FORMULA: 
             dbLinha.append(cabecalho.get(cell.getColumnIndex()), cell.getCellFormula()); 
             break; 
            case Cell.CELL_TYPE_BOOLEAN: 
             dbLinha.append(cabecalho.get(cell.getColumnIndex()), cell.getBooleanCellValue()); 
             break; 
            case Cell.CELL_TYPE_NUMERIC: 
             dbLinha.append(cabecalho.get(cell.getColumnIndex()), cell.getNumericCellValue()); 
             break; 
            default: 
             dbLinha.append(cabecalho.get(cell.getColumnIndex()), cell.getStringCellValue()); 
           } 
          } 

         } 
        } catch (IllegalStateException e) { 
         Log.info(this, "Erro ao obter valor da linha [{}] e coluna [{}]", cell.getRow().getRowNum(), cell.getColumnIndex()); 
        } 
       } 
       if (!dbLinha.isEmpty()) { 
        for(int i = 0; i < cabecalho.size(); i++){ 
         if(!dbLinha.containsKey(cabecalho.get(i))){ 
          dbLinha.append(cabecalho.get(i), " "); 
         } 
        } 
        listLinha.add(dbLinha); 
        dbLinha.clear(); 
       } 
      } 
     } catch (FileNotFoundException e) { 
      Log.error(this, "Erro ao processar planilha: Planilha não encontrada.", e); 
     } catch (IOException e) { 
      Log.error(this, "Erro ao processar planilha.", e); 
     } 
     System.out.println(listLinha.toString()); 
     return listLinha; 
    }

输出