如何创建一组空数组并用用户输入填充并打印出来？

Question

Here is my code to fill an empty array :

package duplicate.terminator;
import java.util.Arrays;
import java.util.Scanner;
public class DuplicateTerminator {
       public static void main(String args []){

           Scanner number = new Scanner(System.in);
           int a, num;
           int[] integerset = null;

                System.out.println("Enter Number: ");
                num = number.nextInt();
                Arrays.fill(integerset, num);

       }

}

That is my code because I want to have this output. I need to stack input numbers in array and print it out like this.

Sample Input/Output:
    Enter number: 5
    5
    Enter number: 9
    5 9
    Enter number: 2
    5 9 2
    Enter number: 9
    9 has already been entered
    5 9 2
    Enter number: 1
    5 9 2 1

Answer 1

I would suggest using LinkedHashSet

because

• you don't know the number of elements in your data container initially
• you don't want duplicates and you don't want to go serially to check if there is a duplicate
• you want to preserve order

Here is an example:

Set<Integer> numbers = new LinkedHashSet<>();

while(/*some logic to exit on special input*/) {
   if(!numbers.add(userInputNum){
     // number was already present
   }
}

Answer 2

If you don't want to use LinkedHashSet or fill method in array this is an alternate way to do it.

public static void main(String[] args) 
{
    Scanner scan = new Scanner(System.in);
    int i, j;
    int[] list = new int[10];
    for (i = 0; i <= 9; i++)
    {
        System.out.println("Enter a number :");
        list[i] = scan.nextInt();
        for (j = 0; j < i; j++)
        {
            if (list[j] == list[i])
            {
                System.out.println(list[j] + " has already been entered");
                i--;
            }
        }
        for(j = 0; j <= i; j++)
        {
            System.out.print(list[j] + " ");
        }
        System.out.println();

    }
}