Convert (ArrayLists) in java android

Question

If I have Arraylist<Integer> how can I do convert it to ArrayList<String>

final ArrayList<Integer> arrayList = 
    new ArrayList<Integer>(asList(19,85,955,9,2,62,96,2,6,26,2,26,2));

the Toast did not print any think on the Screen

ListView listView=findViewById(R.id.arraylistv);
     final ArrayList<Integer> arrayList=new ArrayList<Integer>(asList(19,85,955,9,2,62,96,2,6,26,2,26,2));
    final ArrayAdapter< Integer> arrayAdapter =new ArrayAdapter<Integer>(this , android.R.layout.simple_list_item_activated_1,arrayList);
    listView.setAdapter(arrayAdapter);
    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

            Toast.makeText(getApplicationContext(),"your num is  "+arrayList,Toast.LENGTH_LONG);
        }
    });

What do you mean? As flakes said it is already an ArrayList? How do you convert an int to an int? — Ishaan Javali
– Ishaan Javali, Commented Nov 23, 2018 at 21:41
Do you mean how to populate a List with values using asList? Then you miss the static import java.util.Arrays. — Glains
– Glains, Commented Nov 23, 2018 at 21:43
target array contains String and not Integer? you maybe could try something like that : 'listInt.stream.map(String::valueOf).collect(Collectors.toList())' — boly38
– boly38, Commented Nov 23, 2018 at 22:18
what have you tried so far ? where is your code ? switching from Integer to String is very well documented all over the internet, did you search into the java doc or java online courses ? — LoneWanderer
– LoneWanderer, Commented Nov 23, 2018 at 22:39

Krease · Accepted Answer · 2018-11-23 22:20:12Z

4

You can use streams to easily convert type of a List, like this:

List<Integer> input = Arrays.asList(19,85,955,9,2,62,96,2,6,26,2,26,2);
List<String> result = input.stream().map(String::valueOf).collect(Collectors.toList());

In this case, we're using map to convert each element using String::valueOf - which basically is a function that converts the input into a string. You can replace this with any other function to convert the input type to other types.

answered Nov 23, 2018 at 22:20

Krease

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1 Comment

flakes Over a year ago

If you really need to to be an ArrayList you can also do input.stream().map(String::valueOf).collect(Collectors.toCollection(ArrayList::new))

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