将每个循环的增强型转换为流 java 8

Question

I am trying to convert code written in enhanced for each loop to streams in java. Here is my traditional code

    List<OrderDetail> orderDetails = new ArrayList<>();
    if (arInvoiceOrderResponseBody != null) {
        if (arInvoiceOrderResponseBody.getOrders() != null && 
         arInvoiceOrderResponseBody.getOrders().size() > 0) {
         for (OrderDetail orderDetail : arInvoiceOrderResponseBody.getOrders()) {
                if (orderDetail != null) {
                    if (orderDetail.getStatusHistory() != null && 
                        orderDetail.getStatusHistory().size() > 0) {
                        for (StatusHistory statusHistory : orderDetail.getStatusHistory()) {
                            if (statusHistory != null) {
                                if (statusHistory.getStatusCode() != null) {
                                    if (statusHistory.getStatusCode().equals("POD")) {
                                        orderDetail.setStatusDateTime(statusHistory.getStatus_date_time());
                                    }
                                }

                            }
                        }
                    }
                }
                orderDetails.add(orderDetail);
            }
            arInvoiceOrderResponseBody.setOrders(orderDetails);
        }

Can anyone help me on replicating same functionality through streams.Any help would be greatly helpful

This is what i am trying

    arInvoiceOrderResponseBody.getOrders().stream() .flatMap(order ->
    order.getStatusHistory().stream()) 
    .filter(statusHistory ->statusHistory.getStatusCode().equals("POD"))
    //Here if condition is true then i need to do this.I need to set one
    //of the property of main order object to one of the property of status 
    //history object 
    //order.setStatusDateTime(statusHistory.getStatus_date_time());

Answer 1

Following is about as Java-8 as this is going to get in my opinion.

arInvoiceOrderResponseBody.getOrders().forEach(
      orderDetail -> orderDetail.getStatusHistory().stream()
        .filter(statusHistory -> "POD".equals(statusHistory.getStatusCode()))
        .findFirst()
        .ifPresent(statusHistory -> orderDetail.setStatusDateTime(statusHistory.getStatus_date_time()))
    );

I note the original code changes the existing OrderDetail instances but then puts them (all) into a new collection and replaces the original collection. This seems pointless on the face of it!

Answer 2

Splitting it out into multiple methods and breaking it down into two streams may work. Something like:

  public static ResponseBody processResponseBody(ResponseBody responseBody)
  {
    if(validate(responseBody))
    {
      List<OrderDetail> orderDetails = responseBody.getOrders().stream()
          .filter(od -> validate(od))
          .map(od -> processOrderDetail(od))
          .collect(Collectors.toList());
      responseBody.setOrders(orderDetails);
    }
    
    return responseBody;
  }
  
  private static OrderDetail processOrderDetail(OrderDetail orderDetail)
  {
    StatusHistory statusHistory = orderDetail.getStatusHistory().stream()
          .filter(sh -> validate(sh))
          .findFirst()
          .orElseThrow(() -> new IllegalArgumentException("No Status History Found"));
    orderDetail.setStatusDateTime(statusHistory.getStatus_date_time());

    return orderDetail;
  }
  
  private static boolean validate(ResponseBody responseBody)
  {
    return responseBody != null && responseBody.getOrders() != null && responseBody.getOrders().size() > 0;
  }
  
  private static boolean validate(OrderDetail orderDetail)
  {
    return orderDetail != null && orderDetail.getStatusHistory() != null && orderDetail.getStatusHistory().size() > 0;
  }
  
  private static boolean validate(StatusHistory statusHistory)
  {
    return statusHistory != null && statusHistory.getStatusCode() != null && statusHistory.getStatusCode().equals("POD");
  }

I broke it into a stream to process the OrderDetail object and a stream to reduce the StatusHistory to a single object. I also broke the validation into their own methods for brevity and organization.