如何在Java中将列表字符串列表转换为列表整数列表

Question

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();
        }
    }
} 

Answer 1

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());

Answer 2

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);
}

Answer 3

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);
        }

Answer 4

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);
}