Question

Suppose I have a generic class with a generic parameter T which is a Number subclass. I would like to initialize an array of T during class construction. Is it possible? If yes how? If not why?

public class AClass<T extends Number>{

    private T array[];
    private int arrayOfInt[];

    public AClass(int size){
        arrayOfInt = new int[size];
        array = ? //what should I put here?
    } 
} 

Answer 1

T is only know at compile time. It is not know at runtime and thus you cannot initilise the contents of the array. However you can create the array, every value will be null.

array = (T[]) new Number[size];

EDIT: The problem with creating instances of any type is you need to know what is the default value you want and which constructor you want to call. e.g. there is no new Double()

As mentioned below, double[] will be more efficient and faster than Number[] and unless you need large long values, it will be able to store every possible value.