Split Comma Separated Values in Java, Int and String

Convert a list of integers into a comma-separated string

Yes. However, there is no Collectors.joining for a Stream<Integer>; you need a Stream<String> so you should map before collecting. Something like,

System.out.println(i.stream().map(String::valueOf)
        .collect(Collectors.joining(",")));

Which outputs

1,2,3,4,5

Also, you could generate Stream<Integer> in a number of ways.

System.out.println(
        IntStream.range(1, 6).boxed().map(String::valueOf)
               .collect(Collectors.joining(","))
);

How to split a comma-separated string?

You could do this:

String str = "...";
List<String> elephantList = Arrays.asList(str.split(","));

Basically the .split() method will split the string according to (in this case) delimiter you are passing and will return an array of strings.

However, you seem to be after a List of Strings rather than an array, so the array must be turned into a list by using the Arrays.asList() utility. Just as an FYI you could also do something like so:

String str = "...";
ArrayList<String> elephantList = new ArrayList<>(Arrays.asList(str.split(","));

But it is usually better practice to program to an interface rather than to an actual concrete implementation, so I would recommend the 1st option.

convert comma separated string to list without intermediate container

If you're using Java 8, you can:

int[] numbers = Arrays.asList(numbersArray.split(",")).stream()
  .map(String::trim)
  .mapToInt(Integer::parseInt).toArray();

If not, I think your approach is the best option available.

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