Need help getting populating array with random numbers 1-10 without using 0 in Java

Question

Need help getting populating array with random numbers 1-10 without using 0. - Create an array of 100 integers. I've tried int random = r.nextInt(High-Low) + Low; but that throws off the count of how many of each number.

What I need to do in my assignment:

Populate the array with random numbers ranging from 1 to 10. (not zero)
Determine what the average is of all the numbers in the array.
Count the occurrence of each of the ten numbers in the array of 100. Do by having a second array that's 10 integers in size and increment each element of the array based on the number of duplicates you find in your array of 100 integers.

package arrays;

import java.util.Arrays;
import java.util.Random;

public class Intergers {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        Random r = new Random();

        // Create an array of 100 integers.
        int array[] = new int[100];

        int a = 0;

        // Populate the array with random numbers ranging from 1 to 10.
        while (a < 100)
        {
            int random = r.nextInt(10);
            array[a] = random;
            a++;
        }

        //calculate sum of all array elements
        int sum = 0;

         for(int i=0; i < array.length ; i++)
             sum = sum + array[i];

        //calculate average value
         double average = (double)sum/array.length;

        System.out.println("Array: " + Arrays.toString(array));
        // System.out.println("Sum: " + sum);
         //System.out.println("Array Length: " + array.length);
         System.out.println("Average value of array is: " + average);

         // Count the occurrence of each of the ten numbers in the array of 100
         int[] occurrences = new int[10];
         for (int b : array) {
                occurrences[b]++;
            }
         // System.out.println("Array: " + Arrays.toString(occurrences));



          System.out.println(1 + " appeared " + occurrences[0] + " times");
          System.out.println(2 + " appeared " + occurrences[1] + " times");
          System.out.println(3 + " appeared " + occurrences[2] + " times");
          System.out.println(4 + " appeared " + occurrences[3] + " times");
          System.out.println(5 + " appeared " + occurrences[4] + " times");
          System.out.println(6 + " appeared " + occurrences[5] + " times");
          System.out.println(7 + " appeared " + occurrences[6] + " times");
          System.out.println(8 + " appeared " + occurrences[7] + " times");
          System.out.println(9 + " appeared " + occurrences[8] + " times");
          System.out.println(10 + " appeared " + occurrences[9] + " times");




    }
}

"but that throws off the count of how many of each number" - in what way? (Bear in mind you either need `high - low + 1` or you need `high` to be exclusive...) — Jon Skeet, Sep 29 '15 at 07:09
This is answered already: [http://stackoverflow.com/questions/363681/generating-random-integers-in-a-range-with-java](http://stackoverflow.com/questions/363681/generating-random-integers-in-a-range-with-java) — A.Panzer, Sep 29 '15 at 07:15

Eran · Accepted Answer · 2015-09-29T07:24:57.510

4

int random = r.nextInt(10);

would give you a pseudo-random int between 0 and 9. Just add 1 to get a range between 1 and 10 :

int random = r.nextInt(10) + 1;

You must also adjust your handling of the occurrences array to account for the fact that array indices start at 0 :

     int[] occurrences = new int[10];
     for (int b : array) {
         occurrences[b-1]++;
     }

     for (int i = 0; i < occurences.length; i++) {
         System.out.println(i+1 + " appeared " + occurrences[i] + " times");
     }

edited Sep 29 '15 at 07:24

answered Sep 29 '15 at 07:09

Eran

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Doing that gives me Thread [main] (Suspended (exception ArrayIndexOutOfBoundsException)) Intergers.main(String[]) line: 47 on 'occurrences[b]++;' and doing 'int High = 10; int Low = 1; int random = r.nextInt(High-Low) + Low;' gives me this http://pastebin.com/EvvpREq6 – Ryan Mills Sep 29 '15 at 07:21
@RyanMills That's a separate problem with the way you handle the `occurrences` array. See edit – Eran Sep 29 '15 at 07:23

score 0 · Answer 2 · answered Sep 29 '15 at 09:23

I have an amateur way of doing this.

create an arraylist containing 1-9
create an array to store 100 integers
iterate through the storage array and store the first item after a shuffle of the arraylist

implementation:

    ArrayList<Integer> a = new ArrayList<>();
    for (int i = 1; i < 10; i++) {
        a.add(i);
    }
    int[] store = new int[100];
    for (int i = 1; i < 100; i++) {
        Collections.shuffle(a);            
        store[i] = a.get(0);

    }

Need help getting populating array with random numbers 1-10 without using 0 in Java

2 Answers2