Converting an int array to a String array

Question

So I have this \"list\" of ints. It could be a Vector, int[], List, whatever.

My goal though is to sort the

Answer 1

Use a Stream which is available from Java 8. To get a Stream instance with "list" of ints:

• For int[]
  • IntStream intStream = Arrays.Stream(nums); or
  • Stream<Integer> intStream = Arrays.Stream(nums).boxed(); if you need the same class as bottom one.
• For any classes with Collection<Integer> interface (ex. Vector<Integer>, List<Integer>)
  • Stream<Integer> intStream = nums.stream();

Finally, to get a String[]:

String[] answer = intStream.sorted().mapToObj(String::valueOf).toArray(String[]::new);

Answer 2

If you use a TreeSet, I have a (longish) one-liner for you (assuming items is the TreeSet):

final String[] arr =
    items.toString() // string representation
        .replaceAll("\\D+", " ") // replace all non digits with spaces
        .trim() // trim ends
        .split(" "); // split by spaces

Test code:

Set<Integer> items = new TreeSet<Integer>(Arrays.asList(5, 1, 2, 11, 3));

// insert above code here

System.out.println(Arrays.toString(arr));

Output:

[1, 2, 3, 5, 11]

---

EDIT:

OK, here is a different version that works with the int array directly. But unfortunately it's not a one-liner. However, it does keep duplicates and it's probably faster

EDIT again:

Bug fixed and negative numbers supported, as requested:

EDIT once more: only one regex pass and no trim

    final int[] in = { 5, 1, 2, 11, 3, 2, -5 }; // with duplicate
    Arrays.sort(in);
    final String[] out =
        Arrays.toString(in)
            .replaceAll("(?:\\[?)([-\\d]+)(?:\\]?)", "$1") // just remove [ and ]
            .split("\\s*,\\s*"); // split by comma

    System.out.println(Arrays.toString(out));

Output:

[-5, 1, 2, 2, 3, 5, 11]

Or completely without regex (apart from split()), but with one more step added:

final int[] in = { 5, 1, 2, 11, 3, 2, -5 }; // with duplicate
Arrays.sort(in);
final String stringRep = Arrays.toString(in);
final String[] out =
    stringRep.substring(1, stringRep.length() - 1).split("\\s*,\\s*");

System.out.println(Arrays.toString(out));

Output:

[-5, 1, 2, 2, 3, 5, 11]

Update: stripped whitespace from my last two solutions, hope you're happy now :-)