I have a List something like this:
List<String> name = [[tom,john,peter,richered][manoj,satya,sachin,andrew]]
How would I convert it into a single ArrayList, using stream
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Possible Duplicate : stackoverflow.com/questions/10910312/…Harshit kyal– Harshit kyal2017-12-26 09:12:35 +00:00Commented Dec 26, 2017 at 9:12
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1Downvote for posting non-compiling sample code without specifying input and output and then complaining the answers do not fit.luk2302– luk23022017-12-26 09:47:52 +00:00Commented Dec 26, 2017 at 9:47
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2 Answers
You can use flatMap in Java8,
List<List<String>> main = new ArrayList<>();
List<String> l1 = Arrays.asList("1", "2");
List<String> l2 = Arrays.asList("3", "4");
main.add(l1);
main.add(l2);
List<String> ans = main.stream()
.flatMap(list -> list.stream())
.collect(Collectors.toList());
System.out.println(ans);
OUTPUT
[1, 2, 3, 4]
8 Comments
Sanat Singh
In case if you don't know the input that you are entering asList, how would you achieve this output.
Akash Thakare
This is just to prepare lists quickly for example. Notice the important part where list of list is processed to get list named
ans.Sanat Singh
ans is absolutely fine, but its not relevant to my code: consider this again [[tom,john,peter,richered][manoj,satya,sachin,andrew]] here I can separate these lists into sublist but I would not be use subList in the code provided by you.
Akash Thakare
Okay. Can you add more code or explanation to your question, please? It'll be really helpful to track down the exact problem.
Sanat Singh
Alright, your code is absolute fine, earlier I was using substrings and when I was adding them to the array list using add(subString), it was giving me compile time error, now I realize I don't have to use substrings I only need to use the stream one code. My Apology and thanks for your help.
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Use flatMap:
List<List<String>> name = Lists.newArrayList(Lists.newArrayList("a", "b", "c", "d"), Lists.newArrayList("e", "f", "g"));
List<String> namesTogether = name.stream().flatMap(Collection::stream).collect(Collectors.toList());
System.out.println(namesTogether);
[a, b, c, d, e, f, g]
3 Comments
Sanat Singh
Answer is not relevant to my question, please consider other comments
luk2302
@SanatSingh No, I will not "consider other comments", this is the exact answer to your question. This (in the same way as the other answer) "converts a list having sub-lists into a single list using java 8 streams".
Sanat Singh
Alright, your code is absolute fine, earlier I was using substrings and when I was adding them to the array list using add(subString), it was giving me compile time error, now I realize I don't have to use substrings I only need to use the stream one code. please accept my apology and thanks for your help.