Convert Arraylist to an ArrayList or Integer Array [closed]

Answer 1

You're trying to cast an array of ArrayList objects to an int. Of course you get an error.

First of all, you want a plain old ArrayList, not an array of ArrayLists.

Second, you use Integer.parseInt() to turn String objects into ints. int is a primitive type, not a class type, and certainly not a superclass of String.

Answer 2

Iterator on the list and parse them into Integers:

(WARN: not tested)

ArrayList<String> strArrayList;
int[] ArrayRes = new int[strArrayList.size()];

int i = 0;
for (String s : strArrayList)
{
    ArrayRes[i++] = Integer.parseInt(s);
}

You can then convert them to a single int value based on how you wish to concatenate them.

Answer 3

Define a method which will convert all String value of arraylist into integer.

private ArrayList<Integer> getIntegerArray(ArrayList<String> stringArray) {
        ArrayList<Integer> result = new ArrayList<Integer>();
        for(String stringValue : stringArray) {
            try {
                //Convert String to Integer, and store it into integer array list.
                result.add(Integer.parseInt(stringValue));
            } catch(NumberFormatException nfe) {
               //System.out.println("Could not parse " + nfe);
                Log.w("NumberFormat", "Parsing failed! " + stringValue + " can not be an integer");
            } 
        }       
        return result;
    }

And simply call that method, as

ArrayList<Integer> resultList = getIntegerArray(strArrayList); //strArrayList is a collection of Strings as you defined.

Happy coding :)

Answer 4

You can cast list of strings to ints like this:

ArrayList<Integer> numbers = new ArrayList<Integer>();

for(int i = 0; i < strArrayList.size(); i++) {
   numbers.add(Integer.parseInt(strArrayList.get(i)));   
}

Answer 5

How about this one

   import java.util.ArrayList;
    import java.util.Arrays;
    import java.util.List;

    public class sample7 
    {
        public static void main(String[] args)
        {

            ArrayList<String> strArrayList = new ArrayList<String>();
            strArrayList.add("1");
            strArrayList.add("11");
            strArrayList.add("111");
            strArrayList.add("12343");
            strArrayList.add("18475");
            List<Integer> newList = new ArrayList<Integer>(strArrayList.size()) ;
            for (String myInt : strArrayList) 
            { 
              newList.add(Integer.valueOf(myInt)); 
            }
            System.out.println(newList);
        }

    }