Input an array of unknown size in java

Question

How do I input an array whose length may vary? The input is space delimited and ends when I press enter

public class ArrayInput {
    public static void main(String args[]){
        ArrayList<Integer> al = new ArrayList<Integer>();
        Scanner sc = new Scanner(System.in);
        while(){//what condition to use here?
            al.add(sc.nextInt());
        }
    }
}

An example would be:

1 2 5 9 7 4  //press enter here to mark end of input

Answer 1

Since all your input is in a single line, you can read the entire line and then split it to integers :

String line = sc.nextLine();
String[] tokens = line.split(" ");
int[] numbers = new int[tokens.length];
for (int i=0; i<numbers.length;i++)
    numbers[i] = Integer.parseInt(tokens[i]);

Answer 2

Read the entire line using sc.nextLine() and then split() using \\s+. This way, you don't have to worry about size of input (number of elements). Use Integer.parseInt() to parse Strings as integers.