Converting an int array to a String array

user_1913845 0
Viewed 79763

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

My goal though is to sort the ints and end up with a String[]. How the int array starts out as is up in the air.

ex: Start with:{5,1,2,11,3} End with: String[] = {"1","2","3","5","11"}

Is there anyway to do this without a for loop? I have a for loop now for collecting the ints. I would rather skip doing another for loop.

int list arrays java
14 Answers

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);
user_38997280

Using Eclipse Collections MutableIntList:

String[] result = IntLists.mutable.with(5, 1, 2, 11, 3)
        .sortThis()
        .collect(Integer::toString)
        .toArray(new String[]{});

Assert.assertArrayEquals(
        new String[]{"1", "2", "3", "5", "11"}, result);

Or trading some readability for potential efficiency:

MutableIntList intList = IntLists.mutable.with(5, 1, 2, 11, 3).sortThis();
String[] result = intList.injectIntoWithIndex(
        new String[intList.size()], 
        (r, each, index) -> {
            r[index] = Integer.toString(each);
            return r;
        });

Assert.assertArrayEquals(
        new String[]{"1", "2", "3", "5", "11"}, result);

Note: I am a committer for Eclipse Collections

user_15704150

We can solve this problem using regular expression as follows:

int[] intArray = {1, 2, 3, 4, 5, 6, 7, 8};
String str = new String(Arrays.toString(intArray));
String stripNoneDigits= str.replaceAll("[^\\d]", "");
String[] stringArray = stripNoneDigits.split("");
user_58501210

Java 8 way, no loops at all:

 // Given
int[] array         = {-5, 8, 3, 10, 25};
// When
String[] actual = Arrays.stream(array)
        .sorted()
        .mapToObj(String::valueOf)
        .toArray(String[]::new);
// Then
String[] expected = {"-5", "3", "8", "10", "25"};

assertArrayEquals(expected, actual);
user_27508450
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