Convert Comma Separated Values to List

Question

Assume I have a set of numbers like 1,2,3,4,5,6,7 input as a single String. I would like to convert those numbers to a List of Long objects ie List<Long>.

Can anyone recommend the easiest method?

score 63 · Answer 1 · edited Dec 01 '21 at 22:51

You mean something like this?

String numbers = "1,2,3,4,5,6,7";

List<Long> list = new ArrayList<Long>();
for (String s : numbers.split(","))
    list.add(Long.parseLong(s));

System.out.println(list);

Since Java 8 you can rewrite it as

List<Long> list = Stream.of(numbers.split(","))
        .map(Long::parseLong)
        .collect(Collectors.toList());

Little shorter versions if you want to get List<String>

List<String> fixedSizeList = Arrays.asList(numbers.split(","));
List<String> resizableList = new ArrayList<>(fixedSizeList);

or one-liner

List<String> list = new ArrayList<>(Arrays.asList(numbers.split(",")));

This answer is super old, but still relevant and should be the accepted answer. — cautionbug, May 18 '21 at 16:14

Unihedron · Answer 2 · 2016-07-06T03:11:14.610

11

Simple and handy solution using java-8 (for the sake of completion of the thread):

String str = "1,2,3,4,5,6,7";
List<Long> list = Arrays.stream(str.split(",")).map(Long::parseLong).collect(Collectors.toList());

System.out.println(list);
[1, 2, 3, 4, 5, 6, 7]

Even better, using Pattern.splitAsStream():

Pattern.compile(",").splitAsStream(str).map(Long::parseLong).collect(Collectors‌.toList());

edited Jul 06 '16 at 03:11

answered Dec 16 '14 at 11:15

Unihedron

10,601
13
59
69

score 3 · Answer 3 · answered Jun 15 '12 at 14:11

3

String input = "1,2,3,4,5,6,7";
String[] numbers = input.split("\\,");
List<Integer> result = new ArrayList<Integer>();
for(String number : numbers) {
    try {
        result.add(Integer.parseInt(number.trim()));
    } catch(Exception e) {
        // log about conversion error
    }
}

answered Jun 15 '12 at 14:11

alexey28

5,040
1
19
25

Is there is any utility method availalble in java or apache commons or any other to get the results in a simple way by calling a method? – Kathir Jun 15 '12 at 14:30
You can use some appache or guava collections based on visitor pattern to convert String to Integer, but it will not make code simple. It will make it is harder to read. – alexey28 Jun 15 '12 at 14:34

score 2 · Answer 4 · edited Sep 14 '17 at 15:07

2

You can use String.split() and Long.valueOf():

String numbers = "1,2,3,4,5,6,7";
List<Long> list = new ArrayList<Long>();
for (String s : numbers.split(","))
    list.add(Long.valueOf(s));

System.out.println(list);

edited Sep 14 '17 at 15:07

Jonathan

19,557
6
64
67

answered Oct 28 '14 at 00:02

Unihedron

10,601
13
59
69

score 1 · Answer 5 · edited Dec 01 '21 at 22:37

1

If you're not on java8 and don't want to use loops, then you can use Guava

List<Long> longValues = Lists.transform(Arrays.asList(numbersArray.split(",")), new Function<String, Long>() {
                @Override
                public Long apply(String input) {
                    return Long.parseLong(input.trim());
                }
            });

As others have mentioned for Java8 you can use Streams.

List<Long> numbers = Arrays.asList(numbersArray.split(","))
                      .stream()
                      .map(String::trim)
                      .map(Long::parseLong)
                      .collect(Collectors.toList());

edited Dec 01 '21 at 22:37

codersl

2,144
4
28
32

answered Apr 28 '16 at 07:25

Kishore Bandi

5,237
2
29
47

Instead of `Arrays.asList(numbersArray.split(",")).stream()`, simply `Arrays.stream(numbersArray.split(","))` or `Stream.of(numbersArray.split(","))` can be used. – Utku Özdemir Apr 28 '16 at 22:12
@UtkuÖzdemir actually cant. In that case Lists.transform cannot be used to convert the String to Long. – Kishore Bandi Apr 29 '16 at 03:51
I mean the java8 solution, not the guava one. – Utku Özdemir Apr 29 '16 at 06:19

score 0 · Answer 6 · answered Jul 06 '21 at 10:11

I've used the following recently:

import static com.google.common.collect.ImmutableList.toImmutableList;
import com.google.common.base.Splitter;
import com.google.common.collect.ImmutableList;
...

    final ImmutableList<Long> result = Splitter.on(",")
        .trimResults()
        .omitEmptyStrings()
        .splitToStream(value)
        .map(Long::valueOf)
        .collect(toImmutableList());

This uses Splitter from Guava (to handle empty strings and whitespaces) and does not use the surprising String.split().

score -14 · Accepted Answer · answered Jun 15 '12 at 14:09

-14

I would use the excellent google's Guava library to do it. String.split can cause many troubles.

String numbers="1,2,3,4,5,6,7";
Iterable<String> splitIterator = Splitter.on(',').split(numbers);
List<String> list= Lists.newArrayList(splitIterator );

answered Jun 15 '12 at 14:09

jocelyn

718
5
12

3

Do not use standard Java (hence not the easiest method), neither solve the problem. – Alessandro Alessandra Dec 16 '14 at 10:12
2

Either this answer is not right or @Kathir question is not right. – Aebsubis Feb 14 '17 at 16:40
1

@jocelyn `String.split can cause many troubles.` Such as....? – Dorian Gray May 30 '20 at 07:55
@DorianGray: https://errorprone.info/bugpattern/StringSplitter – palacsint Jul 06 '21 at 10:12

Convert Comma Separated Values to List

7 Answers7

Linked