Question

I want to print out the array as well as its intersection, and also it doesn't show the time elapsed after 100,000

Missing is: 1,000,000 and 10,000,000

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

public class array_intersect {

public static void main(String[] args)
{
for(int i=1000; i <= 10000000; i= i*10)
{
Integer[] array1 = generate_random_array(i);
Integer[] array2 = generate_random_array(i);

long startTime = System.nanoTime();
get_intersection(array1, array2);
long stopTime = System.nanoTime();
long elapsedTime = stopTime - startTime;
System.out.println("Time elapsed for dataset of " + i + " points : "+ elapsedTime + " in nanoseconds");

}
}

public static Integer[] generate_random_array(int size)
{
Random rand = new Random();
Integer[] return_array = new Integer[size];
for(int i=0;i< size ; i ++)
{
return_array[i] = rand.nextInt(size);
}
return return_array;
}

public static Integer[] get_intersection(Integer[] array1, Integer[] array2)
{
HashSet<Integer> set = new HashSet<>();
set.addAll(Arrays.asList(array1));
set.retainAll(Arrays.asList(array2));

Integer[] intersection = {};
intersection = set.toArray(intersection);

return intersection;

}

}

Answer 1

Its is printing after 100,000 it just takes more time.

As you can see from the above picture, it takes 939930274600 nanoseconds( ~15 mins) for printing 1000,000 data sets. So if you wait it will print all the results.

For printing, the arrays and insection will mess up your console. I will suggest you avoid it but still, I have provided the code(its highlighted) for that.

Program

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

public class Test {

   public static void main(String[] args) {
       for (int i = 1000; i <= 10000000; i = i * 10) {
           Integer[] array1 = generate_random_array(i);
           Integer[] array2 = generate_random_array(i);

           long startTime = System.nanoTime();
           Integer[] intersection=get_intersection(array1, array2);
           long stopTime = System.nanoTime();
           long elapsedTime = stopTime - startTime;
          
          
           System.out.println("Array1: "+Arrays.toString(array1));
           System.out.println("Array2: "+Arrays.toString(array2));
           System.out.println("Intersection: "+Arrays.toString(intersection));
          
           System.out.println("Time elapsed for dataset of " + i + " points : " + elapsedTime + " in nanoseconds");

       }
   }

   public static Integer[] generate_random_array(int size) {
       Random rand = new Random();
       Integer[] return_array = new Integer[size];
       for (int i = 0; i < size; i++) {
           return_array[i] = rand.nextInt(size);
       }
       return return_array;
   }

   public static Integer[] get_intersection(Integer[] array1, Integer[] array2) {
       HashSet<Integer> set = new HashSet<>();
       set.addAll(Arrays.asList(array1));
       set.retainAll(Arrays.asList(array2));

       Integer[] intersection = {};
       intersection = set.toArray(intersection);

       return intersection;

   }

}

If you have any further doubts feel free to comment