将java for loop转换成java 8流

Question

Here is the old code which uses nested for loop to get the value of price and add this value into the PriceResponse object's data list.

  PriceResponse priceResponse = PriceResponse.builder()
          .data(new ArrayList<>())
          .build();

  for (Row row : rows) {
      String price = "0";
      for (Param param : row.getCell()) {
          if (param.getId().equals("1")) {
              price = param.getValue();
          }
      }

      priceResponses.getData().add(DataResponse.builder()
              .result(Result.builder().values(price).build())
              .build());
  }

How to rewrite this code using java streams?

Answer 1

Maybe .streams() is not needed and rows has a method forEach . Maybe row does not have a Collection of cells

rows.forEach(row -> {
        String price = row.getCells().stream()
            .filter(param -> param.getId().equals("1"))
            .map(Param::getValue)
            .findAny().orElse("0");
        priceResponses.getData().add(DataResponse.builder()
          .result(Result.builder().values(price).build())
          .build());
    });

The problem here is that using builders the code already becomes very convoluted. I would keep having a variable price . Here I assume that any cell with an ID "1" suffices; not the last one.

Answer 2

List<DataResponse> data = rows.stream() .map(row -> row.getCell().stream() .filter(param -> "1".equals(param.getId())) .map(Param::getValue) .findAny() .orElse("0")) .map(price -> DataResponse.builder() .result(Result.builder().values(price).build()) .build()) .toList(); // or Collectors.toList() PriceResponse priceResponse = PriceResponse.builder() .data(data) .build();