class Parent { }
class Child extends Parent { }
class Child2 extends Parent { }  

public class ArrayTest {
    public static void main(String[] args) {
        Parent[] arr1 = new Child[3];
        arr1[0] = new Parent(); //1
        arr1[1] = new Child();  //2
        arr1[2] = new Child2(); //3
        arr1[3] = new Child();  //4

        Child2[] arr2 = {new Child2(), new Child2(), new Child2()};
        add(arr2);
    }

    public static void add(Parent[] arr) {
        arr[0] = new Parent(); //5
        arr[1] = new Child();  //6
        arr[2] = new Child2(); //7
        arr[3] = new Child2(); //8
    }
}