Convert Iterable to Array using Guava

Question

I need to return a String array. I use Guava to split the String. Please see the code below

Iterable<String> arrayOfValues =  Splitter.on(";").split(myString);

it returns an Iterable. but i need a String[]. Is there are any way to give Iterator< Element > and convert that to Array[]. Many Thanks

score 40 · Accepted Answer · edited Aug 15 '17 at 05:47

40

Use the Iterables.toArray(Iterable<? extends T> iterable, Class<T> type) method in Guava.

edited Aug 15 '17 at 05:47

Isaac Kwan

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answered Jul 31 '13 at 10:03

Narendra Pathai

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9

Iterables#toArray is not public – guai Aug 27 '15 at 08:46
do you know if is there a single code like like this but without guava? – Aquarius Power Dec 28 '15 at 17:50
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@guai Just for benefit of others, Iterables.toArray without second parameter for type class is private. The method above with this parameter is public. – Breeno Feb 15 '17 at 20:57
The conversion to arr [] is super slow. It takes away all the speed benefit you got.. for ex a 500k split loop (~300 values) which finished in 50ms finishes in about 6000ms when converted to arr [] – Nrj Jun 26 '18 at 18:00

score 22 · Answer 2 · answered Jul 31 '13 at 10:05

22

If you use the plain Java String.split(regex) method, you're fine. It returns a String[].

"my;string".split(";")

String[] splits = mystring.split(";");

Don't use fancy libraries if you don't need them.

answered Jul 31 '13 at 10:05

rec

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score 7 · Answer 3 · answered Aug 16 '18 at 11:00

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In java 8 I prefer to use a stream to convert an iterable to an array:

StreamSupport.stream(yourIterable.spliterator(), false).toArray(String[]::new)

answered Aug 16 '18 at 11:00

Andy Brown

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score 4 · Answer 4 · answered Aug 02 '13 at 15:52

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You can also use Guava's FluentIterable :

FluentIterable.from(Splitter.on(":").split(mystring)).toArray(String.class)

answered Aug 02 '13 at 15:52

Oussama Zoghlami

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score 2 · Answer 5 · answered Mar 07 '18 at 07:20

Without Guava, you could convert an Iterable<String> to an array with something like this

public static <String> String[] toArray(Iterable<String> itr) {
    ArrayList<String> ret = new ArrayList<>();
    for(String t : itr) {
        ret.add(t);
    }
    return ret.toArray(new String[]);
}

It’s a bit hard to write a generic version of this function due to the myriad issues with generic arrays in Java, so tread lightly.

score 0 · Answer 6 · answered Aug 10 '16 at 08:14

In guava you can convert it as Follows

 String test= "Welcome to java world";
 Iterable<String> tokens=Splitter.on(" ").split(test);
 String array[]=Iterables.toArray(tokens,String.class);

If you just want to access the Iterator elements like an array then no need to convert. You can directly access these elements by index

e.g

 System.out.println(Iterables.get(tokens,2));

score 0 · Answer 7 · answered Feb 02 '17 at 06:37

0

Even though the question says "Convert Iterator to Array", answers only explain how to convert Iterable to Array.

So, to convert Iterator to Array with Guava you can use Iterators.toArray(Iterator<? extends T> iterator, Class<T> type).

answered Feb 02 '17 at 06:37

Taylan

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score 0 · Answer 8 · edited Oct 04 '18 at 14:39

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I truly agree with @rec's answer: Don't use fancy libraries if you don't need them.

But, I strongly recommend reading Guava's splitter documentation:

Because java builtin splitter may has some tricky behaviors..

For example, suppose you have trailing commas or successive commas in your input. What will be returned after split?

null
""
(discarded)

;)

edited Oct 04 '18 at 14:39

Vineeth Sai

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answered Oct 04 '18 at 14:31

Enrique S. Filiage

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Errorprone suggest to use `Splitter` instead of `String.split`, see https://errorprone.info/bugpattern/StringSplitter – hywak Dec 21 '21 at 13:34

Convert Iterable to Array using Guava

8 Answers8