CODEWITHSUNDEEP
javacollections
Sathes kumar
Sathes kumar

Reputation: 31

Flatten list of list of strings into single comma separated list

How would I convert a list of list of strings into a single comma separated list (flatten the lists in one)? Eg: 

[[[B1, TMC, Streampix], [HSD1, Streampix - HSD], [CDV1, CDV2]]]

into 

[B1, TMC, Streampix], [HSD1, Streampix - HSD], [CDV1, CDV2]

Upvotes: 2

Views: 1395

Answers (4)

Yassin Hajaj
Yassin Hajaj

Reputation: 21975

It becomes really easy using streams.

Stream over each list, convert it to a string separated by commas and then collect them all in a big list.

List<String> newList = list.stream()
                           .map(x -> x.stream().collect(Collectors.joining(",")))
                           .collect(Collectors.toList());

newList.forEach(System.out::println);

Output

B1,TMC,Streampix
HSD1,Streampix - HSD
CDV1,CDV2

Upvotes: 2

Saurabh Gaur
Saurabh Gaur

Reputation: 23815

Use StringUtils.join() method if you have Apache Commons Lang lib

suppose list has following element

 List list = [[["B1", "TMC", "Streampix"], ["HSD1", "Streampix - HSD"], ["CDV1", "CDV2"]]]

then :

String strList = StringUtils.join(list,',');
System.out.println(strList);

output :

[[B1, TMC, Streampix], [HSD1, Streampix - HSD], [CDV1, CDV2]]

for the reference see link How to convert a List<String> list to csv string

Hope this will help you...:)

Upvotes: 1

Antony Dao
Antony Dao

Reputation: 425

Do you mean this:

//inputList is your List of List of String
List<String> retval = new ArrayList<>();
for(List<String> l : inputList){
    retval.add(l.toString());
}

then the retval = [B1, TMC, Streampix], [HSD1, Streampix - HSD], [CDV1, CDV2]

Upvotes: 0

sbowde4
sbowde4

Reputation: 777

This is actually really simple.

You can actually create an arraylist of arraylists! Then print that out with a loop and it will be in the format you want automatically

Here is an example I think may help you.

ArrayList<ArrayList> list = new ArrayList();//create a list of lists
ArrayList<String> test = new ArrayList();//sample data
ArrayList<String> test2 = new ArrayList();//sample data

test.add("Test");//add sample data to list
test.add("Test");
test.add("Test");
test2.add("Test");
test2.add("Test");
test2.add("Test");

list.add(test);//ad sample lists to main list
list.add(test2);

for (int i = 0; i < list.size(); i++)//this is what you want for your list
    System.out.println(list.get(i));

This has an output of

[Test, Test, Test] [Test, Test, Test] instead of [[Test, Test, Test],[Test, Test, Test]]

Upvotes: 0

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