如何去掉一层list在这段代码中 List<List<PhysicalsPackageEntity>> physicals_package_code1 = list.stream().map(physicalsItemRecordEntity -> { String physicals_package_code = physicalsItemRecordEntity.getPhysicals_package_code(); QueryWrapper<PhysicalsPackageEntity> physicalsPackageEntityQueryWrapper = new QueryWrapper<>(); physicalsPackageEntityQueryWrapper.eq("physicals_package_code", physicals_package_code); List<PhysicalsPackageEntity> physicalsPackageEntityList = this.list(physicalsPackageEntityQueryWrapper); return physicalsPackageEntityList; }).collect(Collectors.toList());

可以使用flatMap方法将List<List<PhysicalsPackageEntity>>转换为List<PhysicalsPackageEntity>，代码如下：

List<PhysicalsPackageEntity> physicalsPackageEntityList = list.stream()
.map(physicalsItemRecordEntity -> {
String physicals_package_code = physicalsItemRecordEntity.getPhysicals_package_code();
QueryWrapper<PhysicalsPackageEntity> physicalsPackageEntityQueryWrapper = new QueryWrapper<>();
physicalsPackageEntityQueryWrapper.eq("physicals_package_code", physicals_package_code);
List<PhysicalsPackageEntity> physicalsPackageEntityList = this.list(physicalsPackageEntityQueryWrapper);
return physicalsPackageEntityList;
})
.flatMap(Collection::stream)
.collect(Collectors.toList());