How can I pass a Class as parameter and return a generic collection in Java?

Question

I am designing a simple Data Access Object for my Java application. I have a few classes (records) that represents a single row in tables like User and Fr

Answer 1

I believe what you are trying to do is possible with a bit of generics magic. I had to solve the same problem just now and this is what I did:

public class ListArrayUtils{
   @SuppressWarnings("unchecked") // It is checked. 
   public static  List filterByType(List aList, Class aClass){
      List ans = new ArrayList<>();
      for(E e: aList){
         if(aClass.isAssignableFrom(e.getClass())){
            ans.add((T)e);
         }
      }
      return ans;
   }       
}

And unit tests:

public class ListArrayUtilsTest{
   interface IfA{/*nothing*/}
   interface IfB{/*nothing*/}
   class A implements IfA{/*nothing*/}
   class B implements IfB{/*nothing*/}
   class C extends A implements IfB{/*nothing*/}

   @Test
   public void testFilterByType(){
      List