Getting back primitive array after insertion into an ArrayList of primitive arrays in Java

Question

List x = new ArrayList();
x.add(new double[]={1,2,3,4,54,6});  

elements 1,2,3,4,54,6 are added to x

Answer 1

This is because the List is being made up of double[] instead of double.

Because a double[] is an array, you have to specify the position from that array as well. Like so:

x.get(0)[0]

If you want to be able to just use x.get(), your List must be made up of double primitives. Then you can add the array of doubles to the List using a separate method (I don't know of one that is built in):

List addArray(List o, double[] a) {
  for(Double d : a)
    o.add(d);

  return o;
}

Hopefully that makes sense. I like using short variable names to make the logic more clear. As long as you know what the variables are, you should be fine.