Iterating through a generic list of unknown type

Question

Hi,
I am in the process of creating pdf reports for my project.I have to deal with a persistence api to get the data for the report.The data will be in the form of a list,like List<SomeObject>,all these lists returned by the persistence framework contains object of some type which implements a common interface.But through that interface I wont be able to get all the data for my reports.So I am looking for a generic way for iterating through the list,by providing some metadata for the data within the list. I am planning to use reflection to query through the list.Is there any feature of generic,through which I can easily iterate through this unknown type,preferrably a combination of reflection and generics,I want to reduce the LOC.Any suggestions??

Answer 1

If the List returned by the framework isn't parameterized, Like
public List<K> getList(Class<K> classType);
then you have to cast it to the appropriate type. If you are not sure about the type of the Objects in the list, and you have a bunch of class types you could expect from the list, then you could use instanceof operator.
If it could be Class A or B, then
if (obj instanceof A){
A castObject = (A) obj;
else if(obj instanceof B){
B castObject = (B)obj;
}Even to do reflection to invoke methods, you need to know the method Names. Which tells me you have the knowledge of what could come out of the list. So cast them. Invoking methods using reflection is really slow.