Cast ArrayList of wrappers to corresponding array of primitives

Question

I use an ArrayList with the wrapper class Short.
After adding some values I want to get the primitive array, but it seems that there is no way with the function toArray(Object[] array), because it need an Array with the wrapper class.

Is there another way without using a for or anything like that?

possible duplicate of [How to convert an ArrayList containing Integers to primitive int array?](http://stackoverflow.com/questions/718554/how-to-convert-an-arraylist-containing-integers-to-primitive-int-array) — Ciro Santilli Путлер Капут 六四事, Mar 26 '15 at 14:09

score 5 · Accepted Answer · answered Jul 11 '11 at 11:05

Apache Commons / Lang has a class ArrayUtils that defines these methods.

All methods called toObject() convert from primitive array to wrapper array.
All called toPrimitive() convert from wrapper object array to primitive array

I think, you need ArrayUtils's toPrimitive()

public static short[] toPrimitive(Short[] array)

Converts an array of object Shorts to primitives.

score 2 · Answer 2 · answered Jul 11 '11 at 11:05

2

Try org.apache.commons.lang.ArrayUtils's toPrimitive(...) method.

answered Jul 11 '11 at 11:05

Thomas

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Just be careful with this, since you are **copying** array two times: first time with `toArray()` and second time with `toPrimitive()`. None of them returns underlying array. – Op De Cirkel Jul 11 '11 at 11:34

score 1 · Answer 3 · answered Jul 11 '11 at 11:06

1

You can fill the array yourself:

ArrayList<Short> shorts = ...;
short shortArray[] = new short[shorts.size()];
for (int i = 0; i < shorts.size(); i++)
   shortArray[i] = shorts.get(i);

Notice that I exploit autoboxing in the assignment line.

answered Jul 11 '11 at 11:06

Mathias Schwarz

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You could use a library as others suggest, but that seems a bit of an overkill to avoid writing three lines of code. – Mathias Schwarz Jul 11 '11 at 11:07
He wanted a solution *without* a for loop. – phlogratos Jul 11 '11 at 11:09
@phlogratos: He doesn't state that anywhere. Also, a library would of course use a for loop in the same way as above, so the loop is just pushed into some library function. – Mathias Schwarz Jul 11 '11 at 11:11
He wrote: `Is there another way without using a for or anything like that?` – phlogratos Jul 11 '11 at 11:18
Ok, I must have misread that sentence. The answer to his question is basically that he needs a for loop, either in a library function or written directly. – Mathias Schwarz Jul 11 '11 at 11:33
Because it is opensource, you can take the parts you need. :) – CSchulz Jul 11 '11 at 12:05

Cast ArrayList of wrappers to corresponding array of primitives

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