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Anoop Dobhal
Anoop Dobhal

Reputation: 107

How to convert List of List String into List of List Integer in java

I have a List of List string, now I want to convert it into List of List Integer. Suggest some way, How to proceed for it?

here is my code:

public class convert {

    public static void main(String[] args) {
        try {

            List<List<String>> outerList = new ArrayList<List<String>>();
            outerList.add(new ArrayList<String>(asList("11","2")));
            outerList.add(new ArrayList<String>(asList("2","1")));
            outerList.add(new ArrayList<String>(asList("11","3")));

            System.out.println(outerList);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Upvotes: 0

Views: 302

Answers (4)

user3453226
user3453226

Reputation:

You will have to iterate over each subItem of each item.

List<List<String>> stringList = new ArrayList<List<String>>(); // Input
List<List<Integer>> intList = new ArrayList<List<Integer>>(); // Output
for (List<String> item : stringList) {
    List<Integer> temp = new ArrayList<Integer>();
    for (String subItem : item) {
        temp.add(Integer.parseInt(subItem));
    }
    intList.add(temp);
}

Upvotes: 1

Rahul Tripathi
Rahul Tripathi

Reputation: 172608

You simply try like this:

for(String s : yourStringList) 
{
  intList.add(Integer.valueOf(s));
}

EDIT

for (List<String> s : yourStringList) {
    List<Integer> x = new ArrayList<Integer>();
    for (String str: s) {
        x.add(Integer.parseInt(str));
    }
    intList.add(x);
}

Upvotes: 3

Marko Topolnik
Marko Topolnik

Reputation: 200266

I woud suggest using the Streams API for this:

import static java.util.stream.Collectors.toList;

...

integerList = outerList.stream()
   .map(innerList->innerList.stream().map(Integer::valueOf).collect(toList()))
   .collect(toList());

Upvotes: 4

user1935024
user1935024

Reputation:

res is new arrayList contains lists of integers. 

       List<List<Integer>> res = new ArrayList<List<Integer>>();

        for(List<String> l : outerList){
            ArrayList<Integer> al = new ArrayList<Integer>();
            for(String s: l){
                al.add(Integer.valueOf(s));
            }
            res.add(al);
        }

Upvotes: 1

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