public class Opgave6{
    public static void main(String args[]){
        Verzameling A = new Verzameling(100, 3);
        System.out.println("\nVerzameling A: " + A);

        Verzameling B = new Verzameling(100, 4);
        System.out.println("\nVerzameling B: " + B);

        boolean b = A.subSet(B);
        System.out.println("\nA subSet of B? " + b);

        Verzameling C = A.intersect(B);
        System.out.println("\nThe intersection of A and B: " + C);

    }
}

import java.util.Random;

class Verzameling{
    int[] elements;
    int amount = 100;
    int x = 0;

    Verzameling(int amount, int seed){
        Random randomGenerator = new Random(seed);
        elements = new int[amount];
        for (int i = 0; i < elements.length; i++){
            elements[i] = i;
        }

        for (int i = 0; i < 20; i++){
            int random = randomGenerator.nextInt(100-i)+i;
            int temp = elements[i];
            elements[i] = elements[random];
            elements[random] = temp;
        }

    }

    Verzameling(int[] elementen){
        this.elements = elements;
    }

    boolean subSet(Verzameling V){
        int x = 0;
        for (int i = 0; i <  20; i++){
            for (int j = 0; j < 20; j++){
                if (this.elements[i] == V.elements[j]){
                    this.x++;
                }
            }
        }
        if (this.x == 20){
            return true;
        }
        else{
            return false;
        }
    }

    Verzameling intersect(Verzameling V){
        int location = 0;
        Verzameling C = new Verzameling(this.x, 0);
        for (int i = 0; i < 20; i++){
            for (int j = 0; j < 20; j++){
                if (this.elements[i] == V.elements[j]){
                    C.elements[j] = this.elements[i];
                    location++;
                }
            }
        }
        return C;
    }

    public String toString(){
        String output = "";
        for (int i = 0; i < 20; i++){
            output = output + elements[i] + " ";
        }
        return output;
    }


}

uitvoer/ error code:

C:\Users\Johan\Documents\Universiteit\Java\pjava\Oopgave6>java Opgave6

Verzameling A: 34 93 22 31 28 47 59 32 19 71 85 14 97 92 61 16 64 41 24 20

Verzameling B: 62 35 45 3 43 5 4 92 22 24 42 52 7 36 70 47 41 49 18 76

A subSet of B? false
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 60
        at Verzameling.<init>(Verzameling.java:18)
        at Verzameling.intersect(Verzameling.java:47)
        at Opgave6.main(Opgave6.java:12)