传统方式:ListUtil.java
public class ListUtil{ private static Logger LOGGER=LoggerFactory.getLogger(ListUtil.class); /** * 分组依据接口,用于集合分组时,获取分组 * T为要groupBy属性是类型,这个返回值为要groupBy的属性值 */ public interface GroupBy<T> { T groupBy(Object obj) ; } /** * 通过属性对集合分组 * @param colls * @param gb * @return * extends Comparable<T> */ public static final <T,D> Map<T ,List<D>> groupBy(Collection<D> colls ,GroupBy<T> gb){ Map<T ,List<D>> map = new HashMap<T, List<D>>(); Iterator<D> iter = colls.iterator() ; while(iter.hasNext()) { D d = iter.next() ; T t = gb.groupBy(d) ; if(map.containsKey(t)) { map.get(t).add(d) ; } else { List<D> list = new ArrayList<D>() ; list.add(d) ; map.put(t, list) ; } } return map ; } /** * 通过属性名称对集合分组 * @param colls * @param fieldName为集合中对象的属性名称 * @return * extends Comparable<T> */ public static final <T,D> Map<T ,List<D>> groupBy(Collection<D> colls ,String fieldName){ return groupBy(colls,new GroupBy<T>(){ @Override public T groupBy(Object obj){ Object v=getFieldValueByName(obj,fieldName); return (T)v; } }); } /** * 根据属性名称获取属性值 * */ public static Object getFieldValueByName(Object o,String fieldName) { try { String firstLetter = fieldName.substring(0, 1).toUpperCase(); String getter = "get" + firstLetter + fieldName.substring(1); Method method = o.getClass().getMethod(getter, new Class[] {}); Object value = method.invoke(o, new Object[] {}); return value; } catch (Exception e) { LOGGER.error(e.getMessage(),e); return null; } }}
参考:https://blog.csdn.net/frankenjoy123/article/details/70739800
java stream:
ReportDetailInfo.java
@Data @ToString public class ReportDetailInfo { private String account; private String orderNo; private String customer; private String courier; private String courierBillNo; private String subscribedDate; // private String bookingNO; }
过滤:
List<ReportDetailInfo> list = ediPdJdbcTemplate.query(sql,new BeanPropertyRowMapper(ReportDetailInfo.class)) ; list.get(0).setCourier(null); //并发流 list = list.parallelStream().filter(r->r.getCourier()!=null).collect(Collectors.toList()); //串行流: list.stream.filter(r->r.gerCourier()!=null).collect(Collectors.toList());
分组:
Map<String, List<ReportDetailInfo>> collect = list.parallelStream().collect(Collectors.groupingBy(ReportDetailInfo::getCourier)); Set<Entry<String, List<ReportDetailInfo>>> entrySet = collect.entrySet(); for (Entry<String, List<ReportDetailInfo>> entry : entrySet) { System.err.println(entry.getKey()+"---> size"+entry.getValue().size() ); }
统计:
参数1:根据那个字段分组参数2:数据统计Map<String, Long> collect = list.parallelStream().collect(Collectors.groupingBy(ReportDetailInfo::getCourier,Collectors.counting())); Set<Entry<String, Long>> entrySet = collect.entrySet(); for (Entry<String, Long> entry : entrySet) { System.err.println(entry.getKey()+"---> size"+entry.getValue() ); }
原文地址:https://www.cnblogs.com/lshan/p/10857019.html
时间: 2024-11-05 22:53:10