Bug: Return value of putIfAbsent is ignored, but list is reused

淡淡的烟草味﹌ 2022-05-23 07:13 151阅读 0赞

这个错误是findbugs插件找出来的问题.

代码首先是这样的

public static List<InvoiceDTO> getKeyInvoiceOpeningResList(
                String key) {
            List<InvoiceDTO>  list = invoiceOpeningListMap.get(key);
            if (list == null) {
                list = new ArrayList<InvoiceDTO>();
                invoiceOpeningListMap.put(key, list);
            }
            return list;
        }

提示Bug: Sequence of calls to java.util.concurrent.ConcurrentHashMap may not be atomic in com..XXX类

参考了网上的信息  修改为

public static List<InvoiceDTO> getKeyInvoiceOpeningResList(
                String key) {
            List<InvoiceDTO>  list = invoiceOpeningListMap.get(key);
            if (list == null) {
                list = new ArrayList<InvoiceDTO>();
                invoiceOpeningListMap.putIfAbsent(key, list);
            }
            return list;
        }

putIfAbsent这个方法在key不存在的时候加入一个值,如果key存在就不放入，等价：

if (!map.containsKey(key)) 
          return map.put(key, value);
      else
           return map.get(key);

解决了多线程同时做这个操作的并发问题

但是改好后依然提示

Bug: Return value of putIfAbsent is ignored, but list is reused in com.XXX类

继续找到https://stackoverflow.com/questions/21251134/how-to-resolve-the-findbug-sequence-of-calls-to-java-util-concurrent-concurrenth

得到答案:

![70][]

要使用返回值

修改如下 findbugs不在报错

public static List<InvoiceDTO> getKeyInvoiceOpeningResList(
                String key) {
            List<InvoiceDTO>  list = invoiceOpeningListMap.get(key);
            if (list == null) {
                list = new ArrayList<InvoiceDTO>();
                list = invoiceOpeningListMap.putIfAbsent(key, list);
            }
            return list;
        }

参考 ：

https://www.cnblogs.com/gaoxing/p/4271749.html

[70]: /images/20220523/d7217cbee9e740148ec63e39ae17d9d7.png