JAVA8 filter对List筛选、排序报nullPointException

最新推荐文章于 2024-03-05 12:29:53 发布

东耳佳茗

最新推荐文章于 2024-03-05 12:29:53 发布

阅读量1.9k

点赞数 1

CC 4.0 BY-SA版权

分类专栏： java8 list 文章标签： java

本文链接：https://blog.youkuaiyun.com/qq_19201215/article/details/115974865

java8 同时被 2 个专栏收录

2 篇文章

订阅专栏

list

1 篇文章

订阅专栏

1、模糊查询，通过ShardsInfoDto.getIndexName()!=null 判断防止indexName为空报空指针异常

String indexName = "asd";
        shardsList = shardsList.stream().filter(ShardsInfoDto -> ShardsInfoDto.getIndexName()!=null&&ShardsInfoDto.getIndexName().indexOf(indexName) > -1).collect(Collectors.toList());
        shardsList.stream().forEach(ShardsInfoDto -> {
            System.out.println(ShardsInfoDto.getIndexName());
        });

2、如果shardsList集合中有null对象，则加入过滤条件Objects::nonNull，这个条件会帮助去除为null的对象

shardsList = shardsList.stream().filter(Objects::nonNull).filter(ShardsInfoDto -> ShardsInfoDto.getIndexName().indexOf(indexName) > -1).collect(Collectors.toList());

3、多个参数联合排序，则加入Comparator.nullsFirst()防止参数为空导致空指针异常！

String docsFlag = "asc";
        String storeFlag = "desc";
        //排序
        Comparator<ShardsInfoDto> doc = null;
        if("asc".equals(docsFlag)){
            //docs升序
            doc = Comparator.nullsFirst(Comparator.comparing(ShardsInfoDto::getDocs, Comparator.nullsFirst(Integer::compareTo)));
        }else if("desc".equals(docsFlag)){
            //docs降序
            doc = Comparator.nullsFirst(Comparator.comparing(ShardsInfoDto::getDocs, Comparator.nullsFirst(Integer::compareTo)).reversed());
        }
        Comparator<ShardsInfoDto> store = null;
        if("asc".equals(storeFlag)){
            //store升序
            store = Comparator.nullsFirst(Comparator.comparing(ShardsInfoDto::getStore, Comparator.nullsFirst(Double::compareTo)));
        }else if("desc".equals(storeFlag)){
            //store降序
            store = Comparator.nullsFirst(Comparator.comparing(ShardsInfoDto::getStore, Comparator.nullsFirst(Double::compareTo)).reversed());
        }
        // 联合排序
        Comparator<ShardsInfoDto> finalComparator = doc.thenComparing(store);
        shardsList.sort(finalComparator);
        for (ShardsInfoDto dto:shardsList) {
            System.out.println("doc:"+dto.getDocs()+",store:"+dto.getStore());
        }