[D cannot be cast to java.lang.Double

Question

I wrote below code. It get this message:

Exception in thread "main" java.lang.ClassCastException: [D cannot be cast to java.lang.Double

double[] xyz = {1, 11, 111, 2, 22, 222};
ArrayList array = new ArrayList();

array.add(xyz);

double[] vals = new double[array.size()];

vals[0] = (double) array.get(0);
vals[1] = (double) array.get(1);
vals[2] = (double) array.get(2);

I have also search and see some post on Stack Overflow, but they do not make much me sense. What should I do?

possible duplicate of [What is a raw type and why shouldn't we use it?](http://stackoverflow.com/questions/2770321/what-is-a-raw-type-and-why-shouldnt-we-use-it) — Minty Fresh, Mar 13 '15 at 14:27
This makes no sense, `array.add(xyz);`. It is of key importance to show us ***exactly*** what you're adding to that ArrayList. You should be using an `ArrayList` regardless. — Hovercraft Full Of Eels, Mar 13 '15 at 14:27
@MintyFresh That is not a duplicate, because the questions are not the same. But it is a related question that the OP should read. — Duncan Jones, Mar 13 '15 at 15:34

Duncan Jones · Accepted Answer · 2015-03-13T15:35:33.620

6

If you want to add an array of double values to an ArrayList, do this:

Double[] xyz = {...};
ArrayList<Double> array = new ArrayList<>(); // note, use a generic list
array.addAll(Arrays.asList(xyz));

A List cannot store primitives, so you must store Double values not double. If you have an existing double[] variable, you can use ArrayUtils.toObject() to convert it.

edited Mar 13 '15 at 15:35

answered Mar 13 '15 at 14:34

Duncan Jones

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score 4 · Answer 2 · edited Mar 13 '15 at 15:11

Actually your problem is that you are trying to cast the type of 'xyz', which does not seems to be a double or the Wrapper associed (Double), into a double.

Since java can't transform the type of 'xyz' into a double a ClassCastException is throw. You should try to add n double to your array like that (or even in a loop) :

ArrayList<Double> myListOfDouble = new ArrayList();
myListOfDouble.add(1.0);

And then using a for loop to populate your double[] vals like this :

for(int i = 0; i < myListOfDouble.size(); i++)
    vals[i] = myListOfDouble.get(i);

[D cannot be cast to java.lang.Double

2 Answers2