11 2020 档案

list一个字段去重
摘要：//按照某个字段去重 public static <T> Predicate<T> distinctByKey(Function<? super T, ?> keyExtractor) { Map<Object, Boolean> seen = new ConcurrentHashMap<>(); 阅读全文
posted @ 2020-11-15 17:00 动力起点 阅读(163) 评论(0) 推荐(0)
list多字段去重
摘要：list = list.stream().collect(Collectors.collectingAndThen(Collectors.toCollection( () -> new TreeSet<>(Comparator.comparing(o -> o.getNewsId() + "#" + 阅读全文
posted @ 2020-11-15 16:50 动力起点 阅读(226) 评论(0) 推荐(0)
mysql按照某一个条件进行分组统计，同时又要保证一个相同字段的数据只统计一次
摘要：SELECT n.pk_id, count( DISTINCT r.user_id ) forwardNum FROM news_info n INNER JOIN news_info_record r ON r.type = 1 AND r.news_id = n.pk_id AND r.data 阅读全文
posted @ 2020-11-11 22:25 动力起点 阅读(2306) 评论(0) 推荐(1)