Join String list elements with a delimiter in one step

Question

Is there a function like join that returns List's data as a string of all the elements, joined by delimiter provided?

 List<String> join; ....
 String join = list.join('+");
 // join == "Elem 1+Elem 2";

or one must use an iterator to manually glue the elements?

gahrae · Answer 1 · 2014-04-09T00:00:50.937

153

Java 8...

String joined = String.join("+", list);

edited Apr 09 '14 at 00:00

answered Apr 08 '14 at 22:12

gahrae

3

Sadly `String.join()` accepts only `Iterable` (apart from varargs) unlike Guava's `Joiner.join()` which accepts `Iterable>`, `Iterator>`, varargs, ... – Venkata Raju Aug 07 '14 at 12:26
7

Correct - String.join() does not handle arbitrary types. It expects an iterable CharSequence, ie List. If you want to delimit arbitrary types then you need to extract the String value and build the delimited list. This is also a one liner in Java 8: `String joined = iterableOfNonCharSequence.stream().map(object -> object.methodToGetStringValue()).collect(Collectors.joining(","));` – gahrae Aug 08 '14 at 04:46
StringJoiner is also a useful class for joining content. Here is an example program showing StringJoiner and Collectors.joining... http://pastebin.com/i2YwJcZy# – gahrae Jul 17 '15 at 18:45
native java solutions > all – fIwJlxSzApHEZIl Jul 21 '17 at 23:26

score 98 · Answer 2 · edited Jan 18 '15 at 15:11

98

You can use the StringUtils.join() method of Apache Commons Lang:

String join = StringUtils.join(joinList, "+");

edited Jan 18 '15 at 15:11

Jared Burrows

answered Oct 26 '10 at 08:26

Romain Linsolas

Of course, creating an utility class is also really easy, if you don't want to use a third-party library for that. But `Apache Commons Lang` provide many usefull methods, that takes care of `null` values... – Romain Linsolas Oct 26 '10 at 08:29

score 19 · Answer 3 · edited Jun 26 '18 at 16:05

19

Or Joiner from Google Guava.

Joiner joiner = Joiner.on("+");
String join = joiner.join(joinList);

edited Jun 26 '18 at 16:05

Steve Chambers

answered Oct 26 '10 at 08:31

nanda

score 4 · Answer 4 · answered Feb 15 '16 at 18:07

4

You can use : org.springframework.util.StringUtils;

String stringDelimitedByComma = StringUtils.collectionToCommaDelimitedString(myList);

answered Feb 15 '16 at 18:07

Karim Oukara

score 3 · Answer 5 · answered Apr 22 '15 at 14:34

3

If you are using Spring you can use StringUtils.join() method which also allows you to specify prefix and suffix.

String s = StringUtils.collectionToDelimitedString(fieldRoles.keySet(),
                "\n", "<value>", "</value>");

answered Apr 22 '15 at 14:34

marcello

1

This can actually be copied and it is a single method: https://gist.github.com/Zhuinden/5d88caee5e184e2b6d5ced329618f086 – EpicPandaForce Jan 16 '17 at 00:29

score 2 · Answer 6 · answered Dec 10 '14 at 11:56

2

If you just want to log the list of elements, you can use the list toString() method which already concatenates all the list elements.

answered Dec 10 '14 at 11:56

Alex G

6 Answers6