Question

I thought that

 Polygon[] polygon = new Polygon[3];

would work. It runs through the ‘new’ line completly fine, but once it hits adding a point, it does a null pointer exeption. I add a point like so (NPEs here)-

polygon[0].addPoint(256, 417);

However, doing it like below works, but I do not want to have a potentially large number of ‘new Polygon()’. Is there a way to do it like my first line of code?

Polygon[] polygon = { new Polygon(), new Polygon(), new Polygon() };

Answer 1

You’d have to do something like this:

Polygon[] polygons = new Polygon[3];
for (int i = 0; i < polygons.length; i++)
{
    polygons[i] = new Polygon();
}

The first line just creates an array – and an array is always filled with null references (or zero values etc). No Polygon objects have been created at this point, which is why you try to use polygons[0].addPoint you’ll get a NullPointerException.

If you want to populate it with references to newly created objects, you need to explicitly create those objects.