Random objects

import java.util.Random;
import java.util.HashMap;
import java.util.function.Supplier;

class A {}
class B {}
class C {}
class D {}

class RandomGenerator {
    private final Supplier[] numbers, generators;
    private final Random rand = new Random();

    RandomGenerator(Supplier[] probabilities) {
        int len = probabilities.length/2;
        numbers = new Supplier[len];
        generators = new Supplier[len];
        for(int i = 0; i < len; i++) {
            numbers[i]    = probabilities[i*2];
            generators[i] = probabilities[i*2+1];
        }
    }

    private double toDouble(Object o) {
        if(o instanceof Integer) return (Integer)o;
        else return (Double)o;
    }

    Object next() {
        double total = 0;
        double[] totals = new double[numbers.length];
        for(int i = 0; i < numbers.length; i++) {
            total += toDouble(numbers[i].get());
            totals[i] = total;
        }
        double rnd = rand.nextDouble() * total;
        int index = 0;
        while(totals[index] < rnd) index++;
        return generators[index].get();
    }
}
public class RandomTest {
    public static void main(String[] args) {
        Supplier[] probabilities = {
            () -> 50, () -> new A(),
            () -> 10, () -> new B(),
            () -> 35, () -> new C(),
            () ->  5, () -> new D()
        };
        RandomGenerator rg = new RandomGenerator(probabilities);
        HashMap<Class, Integer> map = new HashMap<>();

        for(int i = 0; i < 100000; i++) {
            Object o = rg.next();
            map.merge(o.getClass(), 1, (oldNum, x) -> oldNum + 1);
        }

        System.out.println(map);
    }
}