How to get a array[] out of my LinkedList

Question

I need to convert my List:

List<Double> listFoo = new LinkedList<Double>();

to a array of double. So I tried:

double[] foo = listFoo.toArray();

But I get the error:

Type mismatch: cannot convert from Object[] to double[]

How can I avoid this? I could Iterate over the list and create the array step by step, but I don't want to do it this way.

http://stackoverflow.com/questions/960431/how-to-convert-listinteger-to-int-in-java — Alexis C., May 31 '13 at 13:24
http://stackoverflow.com/questions/395030/quick-java-question-casting-an-array-of-objects-into-an-array-of-my-intended-cl — Alex Gittemeier, May 31 '13 at 13:24

Andy Thomas · Answer 1 · 2013-05-31T13:29:23.027

3

You can't make the array of primitives with the standard List class's toArray() methods. The best you can do is to make a Double[] with the generic method toArray( T[] ).

Double[] foo = listFoo.toArray( new Double[ listFoo.size() ] );

One easy way to make a double[] is to use Guava's Doubles class.

double[] foo = Doubles.toArray( listFoo );

edited May 31 '13 at 13:29

answered May 31 '13 at 13:24

Andy Thomas

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score 3 · Answer 2 · answered May 31 '13 at 13:24

You need to make, generic one

Double[] foo = listFoo.toArray(new Double[listFoo.size()]);

That would be the fastest way.

Using new Double[listFoo.size()] (with array size) you will reuse that object (generally it is used to make generic invocation of method toArray).

score 1 · Answer 3 · answered May 31 '13 at 13:24

1

It should work if you make foo an array of Doubles instead of doubles (one is a class, the other a primitive type).

answered May 31 '13 at 13:24

Jesse Craig

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How to get a array[] out of my LinkedList

3 Answers3