记录java常用方法

记录java常用方法

1.取两个集合的差集

public class StreamApiTest {public static void main(String[] args) {List<MktCamCustDetail> batchPos = Arrays.asList(new MktCamCustDetail("123456", 123456L, "张三"),new MktCamCustDetail("345678", 345678L, "王五"),new MktCamCustDetail("234567", 234567L, "赵六"),new MktCamCustDetail("123456", 123456L, "张三"));// 从 batchPos 中提取 objId 列表，去重后直接用于查询List<MktCamCustDetail> mktCamCustDetailList = Optional.ofNullable(batchPos).orElse(Collections.emptyList()) // 防止 batchPos 为 null.stream().map(MktCamCustDetail::getObjId).filter(Objects::nonNull) // 避免包含 null 的 objId.distinct().collect(Collectors.collectingAndThen(Collectors.toList(), StreamApiTest::getMktCamCustDetails));// 取读取到的数据与数据库中已存在的资产的差集，即新增的资产List<MktCamCustDetail> newMktCamCustDetailList = batchPos.stream().filter(m -> mktCamCustDetailList.stream().noneMatch(m2 -> m2.getObjId().equals(m.getObjId()))).collect(Collectors.toList());System.out.println(newMktCamCustDetailList);}/*** 根据 objIdList 查询 MktCamCustDetail 列表** @param objIdList* @return*/public static List<MktCamCustDetail> getMktCamCustDetails(List<String> objIdList) {List<MktCamCustDetail> list = Arrays.asList(new MktCamCustDetail("123456", 123456L, "张三"),new MktCamCustDetail("345678", 345678L, "王五"),// new MktCamCustDetail("234567", 234567L, "赵六"),new MktCamCustDetail("123456", 123456L, "张三"));// 如果 objIdList 为空，直接返回空列表，避免不必要的查询return list;}
}/*** MktCamCustDetail 实体类*/
@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
class MktCamCustDetail {private String objId;private Long custId;private String custName;
}