How can I convert an 2D int array into a 2D String array with Streams?

Question

I am attempting to convert a 2D int array into a 2D String array with this code:

Arrays.stream(intArray).map(a -> 
    Arrays.stream(a).map(i -> 
        Integer.toString(i)).toArray()).toArray(String[][]::new);

but I get the compile-time error cannot convert from String to int when doing Integer.toString(i). I thought it could be because I'm collecting the results of streaming an int array in a String array, but doesn't map create a new Collection?

David Conrad · Accepted Answer · 2017-06-05 22:07:10Z

11

Arrays.stream on an int[] returns an IntStream, and to go from an int to a String or any other Object, you have to use the IntStream.mapToObj method, not the map method:

Arrays.stream(intArray).map(a -> 
    Arrays.stream(a).mapToObj(i -> 
        Integer.toString(i)).toArray(String[]::new)).toArray(String[][]::new);

The map method of IntStream is only used to map from an int to an int.

edited Jun 5, 2017 at 22:07

answered Jun 5, 2017 at 22:01

David Conrad

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