How to add numbers to array in Java?

Question

I'm just learning java, and there is a problem with the array. Well, I want to add all the numbers given by the user to the number array. Only unfortunately, but the code below does not work.

package test;
import java.util.Scanner;


public class testowy {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);


        int number;
        int[]  array = new  int[10];

        do{
            System.out.println("Give a number:");
            number = scanner.nextLine();
            array[number]=s.nextInt();
        }while(number != 0);

    }
}

Answer 1

You don't know how many numbers the user enters so an array is not the best data structure here. A far more elegant solution would be to use a list like so:

    [...]
    List<Integer> numbers = new LinkedList<>();
    do{
       System.out.println("Give a number:");
       number = scanner.nextInt();
       numbers.add(number);
    }while(number != 0);

You could make it work with an array but then you need an additional variable to hold the index, such as in a for-loop. The main mistake in your code is that you mix up indices and values.

Also in this manner, you include the 0, which you may or may not want. If you don't want to include the 0, you can change the do-while loop to a while-loop.

Answer 2

To add an int to something at another arbitrary int location, you can use HashMap

package test;

import java.util.Scanner;
import java.util.Map;
import java.util.HashMap;

public class testowy {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        int number;
        Map<Integer,Integer> map = new HashMap<Integer,Integer>();
        do {
            System.out.print("Give an index: ");
            number = scanner.nextInt();
            System.out.print("\nGive a number: ");
            map.put(number,scanner.nextInt());
            System.out.print('\n');
        } while(number != 0);

    }
}

You can then get an element at index i by calling map. get (i) map. get (i) .

---

To sequentially add an int to a structure, I suggest using an ArrayList .

package test;

import java.util.Scanner;
import java.util.List;
import java.util.ArrayList;

public class testowy {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        int number;
        List<Integer,Integer> list = new ArrayList<Integer>();

        do {
            System.out.println("Give a number:");
            number = scanner.nextInt();
            list.add(number);
        } while(number != 0);

    }
}

You can then get an element at index i the same way, by calling list. get (i) list. get (i) .

Answer 3

I don't know exactly what you try to do because you're mixing the number received with the index of the array, I modified the code:

import java.util.Scanner;
public class Main
{
   public static void main(String[] args) {
       Scanner scanner = new Scanner(System.in);
       int index=0;
       int[]  array = new  int[10];
       int numberInput;
       do{
           System.out.println("Give a number:");
           index++;
           numberInput = scanner.nextInt();
           array[index]=numberInput;
       }while(numberInput != 0);

   }
}

It works and stop when the number received is equals to zero. You can add other condition to stop when index reaches 9, to avoid a exception