repeat elements of string array in java

Question

I have a String array with 4 elements. I want to extend this String array with the same elements repeated 3 or n times.

For Example, for the array

String[] array = {"a", "b", "c", "d"};

I want to have something like

String[] array = {"a", "b", "c", "d", "a", "b", "c", "d", "a", "b", "c", "d" };

I tried to something as follows:

String[] columnHeaderNamesArray = {"A","b","c","d"};
String[] extendedColumnHeaderNamesArray = new String[columnHeaderNamesArray.length * 3];
            Arrays.fill(extendedColumnHeaderNamesArray, columnHeaderNamesArray);

But I got an ArrayStoreException.

Arrays.fill() doesn't treat you array as actually array, it's considered as object. So, you're trying to fill array of string with object of array, it's not allowed. — DDovzhenko
– DDovzhenko, Commented Oct 6, 2017 at 17:29

Mureinik · Accepted Answer · 2017-10-06 17:30:41Z

1

You can use Collections.nCopies to create several copies of the same array, and then flat map them to a single array:

String[] multiplied =
    Collections.nCopies(4, array)
               .stream()
               .flatMap(Arrays::stream)
               .toArray(String[]::new);

answered Oct 6, 2017 at 17:30

Mureinik

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