Java: get type from param and create array of type [duplicate]

Question

Trying to create this:

class Widget
{
  public Widget(Object type)
  {
    Object typeCheck = type.getClass();
    (typeCheck class)[] = new (typeCheck class)[0];
  {
}

Where getting the type of typeCheck and using that to create an array is the troublesome bit. Is there an actual logical way to do this? Or should I just parse the result of getClass() and do it that way?

Use Generics docs.oracle.com/javase/tutorial/java/generics/types.html — Compass
– Compass, Commented Nov 14, 2017 at 17:37
Add a generic type parameter to your Widget class, and use a List rather than an array. (Generics and arrays do not go well together.) — VGR
– VGR, Commented Nov 14, 2017 at 20:20
I'm not permitted to use a List, the point is to correctly the type the Array. — ArchieMoses
– ArchieMoses, Commented Nov 14, 2017 at 20:51

Marcos Vasconcelos · Accepted Answer · 2017-11-14 18:18:23Z

0

Theres a creator in Array class that accepts Class as argument and returns an Object that is a array.

Object typeCheck = type.getClass();
Object[] = (Object[]) new Array.newInstance(typeCheck, 0);

But you cant cast to the generified type captured from getClass() you have to use Object.

So you have three options.

1) Use the properly type if you know all methods

2) Use reflection all the way down

3) Use Generics with a interface, that also will give you compile time methods to call:

class Widget<T extends Component> {
    public Widget(T type) {
      T[] ts = new T[0];
    }
}

answered Nov 14, 2017 at 18:18

Marcos Vasconcelos

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