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? — Ciro Santilli OurBigBook.com
– Ciro Santilli OurBigBook.com, Commented Mar 26, 2015 at 14:09

Saurabh Gokhale · Accepted Answer · 2011-07-11 11:05:39Z

5

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.

answered Jul 11, 2011 at 11:05

Saurabh Gokhale

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Thomas · Accepted Answer · 2011-07-11 11:05:30Z

2

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

answered Jul 11, 2011 at 11:05

Thomas

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1 Comment

Op De Cirkel Over a year ago

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.

Mathias Schwarz · Accepted Answer · 2011-07-11 11:06:27Z

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, 2011 at 11:06

Mathias Schwarz

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6 Comments

Mathias Schwarz Over a year ago

You could use a library as others suggest, but that seems a bit of an overkill to avoid writing three lines of code.

phlogratos Over a year ago

He wanted a solution without a for loop.

Mathias Schwarz Over a year ago

@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.

phlogratos Over a year ago

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

Mathias Schwarz Over a year ago

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.

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