Aug 04

This post is also available in: German

As we already know there is no problem in assigning different Collections on the base-object:

List <Integer> a= new ArrayList<Integer>();

It seem to be clear, that it should work with object-types in the same way, but this is not the case:

import java.util.List;
import java.util.ArrayList;
class Employee{

public static void main(String args[])
{

List <Employee> b = new ArrayList <SalesPerson>(); // CompilerError
SalesPerson a = new SalesPerson();

}

}
class SalesPerson extends Employee{ }

The rule behind is quite easy: declaration of types and transfer need to match exactly, although it is different for arrays;

Employee [ ] c = new SalesPerson[3]; is working without problems – so don’t get confused during certification :)

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