Question

EDIT:
I am trying to add elements read from a txt document line by line into an array list then convert that array list into an array. Although I am getting errors with my code. It doesnt like the int[] a = lines.toArray(new int[lines.size()]);.

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class insertionSort {

public static void main(String[] args) {
    List<Integer> lines = new ArrayList<Integer>();
    File file = new File("10_Random.txt");

    try {

        Scanner sc = new Scanner(file);
        //int line = null;

        while (sc.hasNextLine()) {
            int i = sc.nextInt();
            lines.add(i);
            //System.out.println(i);
        }
        sc.close();
    } 
    catch (FileNotFoundException e) {
        e.printStackTrace();
    }
    int[] a = lines.toArray(new int[lines.size()]);
}
}

Edit2: Thanks chaitanya10! all fixed.

Answer 1

int line= null; is wrong,

“null is a special literal that can be of any object reference type”.you cant assign null to primitive variables in java like (int, byte, float…). null can only be assigned to objects . remember thatnullis the default vale forobjects` when you don’t initialize them.

if you wanna access int as an object use Integer.

Integer line= null;//nowthis would compile

and to convert an list onto array do this.

List.toArray(T[] t) method returns an Object.
do like below.

Integer[] array = lines.toArray(new Integer[lines.size()])

and also your List accepts int[] array and you are tryig to add an int into the list .

change your List declaration like this

List<Integer> lines = new ArrayLis<Integer>();

To print the elements in the array you have to iterate over it

    for(int i=0; i<a.length;i++){
    system.out.println(a[i])
}

you seem to be a beginner in java. strongly recommend you tohereread about java basic