ArrayList of Strings to one single string

Question

I have an array list of strings (each individual element in the array list is just a word with no white space) and I want to take each element and append each next word to the end of a string.

So say the array list has

    element 0 = "hello"
    element 1 = "world,"
    element 2 = "how"
    element 3 = "are"
    element 4 = "you?"

I want to make a string called sentence that contains "hello world, how are you?"

Hi, consider accepting an answer :) – dreamcrash Feb 16 '21 at 09:39 — dreamcrash, Feb 16 '21 at 09:39

score 32 · Answer 1 · answered Jan 11 '16 at 17:46

As of Java 8, this has been added to the standard Java API:

String.join() methods:

String joined = String.join("/", "2014", "10", "28" ); // "2014/10/28"

List<String> list = Arrays.asList("foo", "bar", "baz");
joined = String.join(";", list); // "foo;bar;baz"

StringJoiner is also added:

StringJoiner joiner = new StringJoiner(",");
joiner.add("foo");
joiner.add("bar");
joiner.add("baz");
String joined = joiner.toString(); // "foo,bar,baz"

Plus, it's nullsafe, which I appreciate. By this, I mean if StringJoiner encounters a null in a List, it won't throw a NPE:

@Test
public void showNullInStringJoiner() {
    StringJoiner joinedErrors = new StringJoiner("|");
    List<String> errorList = Arrays.asList("asdf", "bdfs", null, "das");
    for (String desc : errorList) {
        joinedErrors.add(desc);
    }

    assertEquals("asdf|bdfs|null|das", joinedErrors.toString());
}

dreamcrash · Answer 2 · 2020-11-22T09:59:42.407

15

Like suggested in the comments you can do it using StringBuilder:

StringBuilder listString = new StringBuilder();

for (String s : list)
     listString.append(s).append(" ");

or without the explicit loop:

list.forEach(s -> listString.append(s).append(" "));

or even more elegant with Java 8 capabilities:

String listString = String.join(" ", list);

edited Nov 22 '20 at 09:59

answered Dec 04 '12 at 04:04

dreamcrash

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1

this way is the fastest of the mentioned here, btw – WebComer Dec 06 '15 at 23:03

score 13 · Answer 3 · answered Sep 02 '15 at 17:11

Use StringUtils to solve this.

e.g. Apache Commons Lang offers the join method.

StringUtils.join(myList,","))

It will iterate through your array or list of strings and will join them, using the 2nd parameter as seperator. Just remember - there is always a library for everything to make things easy.

score 2 · Answer 4 · edited Jan 05 '18 at 01:43

2

Java 8

final String concatString= List.stream()
                .collect(Collectors.joining(" "));

edited Jan 05 '18 at 01:43

shmosel

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answered Jan 05 '18 at 01:30

Niraj Sonawane

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Why the hyphen? – shmosel Jan 05 '18 at 01:32

score 1 · Answer 5 · answered Dec 04 '12 at 03:27

1

Well, a standard for loop should work:

String toPrint = "";
for(int i=0; i<list.size(); i++){
  toPrint += list.get(i)+" ";
}
System.out.println(toPrint);

Hope that helps!

answered Dec 04 '12 at 03:27

awolfe91

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Just add spaces between the words. – Bhesh Gurung Dec 04 '12 at 03:28
Thanks! Edited to include that. – awolfe91 Dec 04 '12 at 03:29
Also add the "," between "world, how"... just kidding. – dreamcrash Dec 04 '12 at 03:30
Thank you so much! it worked like a charm. now i just have to add the space in there. – user1874239 Dec 04 '12 at 03:33
If he's a beginner, he may as well use something basic. – awolfe91 Dec 04 '12 at 03:59
i am a beginner but id love to learn about it and maybe i can learn enough to use it but i got it working which is what i need. thanks! – user1874239 Dec 04 '12 at 04:00
This does not scale, strings in Java cannot be changed (immutable) so looping around like this might look like it's extending a single string but is actually creating lots of temporary ones. Better to use a StringBuilder. – Gareth Davidson Mar 13 '14 at 15:23

score 1 · Answer 6 · answered Dec 04 '12 at 03:29

1

Simplest way:

String ret = "";
for (int i = 0; i < array.size(); i++) {
    ret += array.get(i) + " ";
}

But if your array is long, performance of string concat is poor. You should use StringBuilder class.

answered Dec 04 '12 at 03:29

TieDad

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thanks for responding. it is assumed that my string is under a certain manageable length. its just for a simple class; nothing too complicated ha – user1874239 Dec 04 '12 at 03:36

score -1 · Answer 7 · answered Feb 18 '14 at 11:21

-1

this is simple method

String value = TextUtils.join(" ", sample);

sample is arraylist

answered Feb 18 '14 at 11:21

Jobin_vibes

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This does not belong to the standard APIs. – qqilihq Feb 18 '14 at 11:30

ArrayList of Strings to one single string

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