Create multiple arrays using a for loop

Question

I would like to make a program where the user can input the number of variables and fill every variable with certain values. For example, the User inputs that he/she wants to make 10 arrays, then the User inputs that the first array should have 5 elements and the User fills that array with values, then the User wants the second array to have 4 elements and does the same and so on.

This is the code I was using, but it doesn't work:

public static void main(String[] args){
    Scanner s = new Scanner(System.in);
    System.out.println("Enter the numbers of variables: ");
    int i = s.nextInt();

    for(int j = 0;j < i;j++){
        int[] var = new int[j];
        System.out.println("Enter the number of values: ");
        int p = s.nextInt();
        for(int q = 0;q < p;p++){
            int n = s.nextInt();
            var[q] = n;
        }
    }
}

And how could I compare these arrays that the user inputs?

you keep trashing var on every iteration, so effectively you only ever have one array. maybe you want an array of arrays... — Marc B
– Marc B, Commented Oct 14, 2016 at 15:17

Community · Accepted Answer · 2017-05-23 12:24:15Z

1

The problem is that each time you are creating the array. try this:

Scanner s = new Scanner(System.in);
System.out.println("Enter the numbers of variables: ");
int i = s.nextInt();
int[][] var = new int[i][];
for(int j = 0;j < i;j++){

    System.out.println("Enter the number of values: ");
    int p = s.nextInt();
    var[j] = new int[p];
    for(int q = 0;q < p;p++){
        int n = s.nextInt();
        var[j][q] = n;
    }
}

Instead of creating a one dimensional array, you create a jagged array. Essentially, a 2d array is an array of arrays. that way the user inputs the number of arrays (i) and then continues to fill the arrays.

To check whether two collections have no commons values, you can use

Collections.disjoint();

For other operations, you can look here

edited May 23, 2017 at 12:24

CommunityBot

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answered Oct 14, 2016 at 15:16

ItamarG3

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5 Comments

progyammer Over a year ago

It should be called a jagged array instead of a 2D array.

Michael Over a year ago

And how could I compare these arrays?

ItamarG3 Over a year ago

Like I said, comparing them depends on their sizes, and is only possible if they are all the same size. In general, comparing arrays is messy.

Michael Over a year ago

I don't point at like comparing, I'm pointing at something like A union B union C or A intersection B

ItamarG3 Over a year ago

@Michael you can accept the answer, so others know it works when they find it.

L. Carbonne · Accepted Answer · 2016-10-14 15:34:07Z

0

This should work (with bidimensionnal array)

    public static void main(String[] args){
        Scanner s = new Scanner(System.in);
        System.out.println("Enter the numbers of variables: ");
        int i = s.nextInt();
        int[][] var = new int[i][];
        for(int j = 0;j < i;j++){
            System.out.println("Enter the number of values: ");
            int p = s.nextInt();
            var[j] = new int[p];
            for(int q = 0;q < p;q++){
                int n = s.nextInt();
                var[j][q] = n;
            }
        }
    }

You have to replace the incrementation in the second loop too ("q++" instead of "p++")

edited Oct 14, 2016 at 15:34

answered Oct 14, 2016 at 15:26

L. Carbonne

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Comments

DarkFenix · Accepted Answer · 2016-10-14 15:40:49Z

0

This should work and solve their first point

    Scanner s = new Scanner(System.in);
    System.out.println("Enter the numbers of variables: ");
    int i = s.nextInt();

    int[][] var = new int[i][];

    for(int j = 0;j < i;j++){
         System.out.println("Enter the number of values: ");
         int p = s.nextInt();
         while (p>0)
         {
            var[j] = new int[p];
            for(int q=0;q < p;q++){
               System.out.println("Value number : " +(q+1) + " For Array Number "+  (j+1));
               int n = s.nextInt();
               var[j][q] = n;
            }
             p-=1;
         }
    }

edited Oct 14, 2016 at 15:40

answered Oct 14, 2016 at 15:33

DarkFenix

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