Choose a random words based on weights

RandomWord.java

import java.util.AbstractCollection;
import java.util.Iterator;
import java.util.Random;
import java.util.Vector;

public class RandomWord {
    public static void main(String []args){
        Vector<Item<String>> words = new Vector<Item<String>>();
        words.add(new Item<String>("Hello", 3));
        words.add(new Item<String>("World", 1));
        words.add(new Item<String>("Mouse", 2));
        words.add(new Item<String>("Cat", 4));
        words.add(new Item<String>("Dog", 8));
        
        test(words, 0, "Hello");
        test(words, 1, "Hello");
        test(words, 2, "Hello");
        
        test(words, 3, "World");
        
        test(words, 4, "Mouse");
        test(words, 5, "Mouse");
        
        test(words, 6, "Cat");
        test(words, 7, "Cat");
        test(words, 8, "Cat");
        test(words, 9, "Cat");
        
        test(words, 10, "Dog");
        test(words, 11, "Dog");
        test(words, 12, "Dog");
        test(words, 13, "Dog");
        test(words, 14, "Dog");
        test(words, 15, "Dog");
        test(words, 16, "Dog");
        test(words, 17, "Dog");
        
        String word = ItemChooser.choose(words);
        System.out.println("Your random word is: " + word);
    }
    
    static void test(AbstractCollection<Item<String>> collection, int num, String expect) {
        String word = ItemChooser.choose(collection, new FixedNumberGenerator(num));
        if(word != expect) {
            System.out.println("Item at " + num + " is not " + expect);
        }
    }
}

class Item<T> {
    public Item(T value, int weight) {
        this.value = value;
        this.weight = weight;
    }
    
    public T value;
    public int weight;
}

class ItemChooser {
    public static <T> T choose(AbstractCollection<Item<T>> collection, NumberGenerator generator) {
        // Step 1: Calculate the weight
        Iterator<Item<T>> iter = collection.iterator();
        int totalWeight = 0;
        while(iter.hasNext()) {
            totalWeight += iter.next().weight;
        }
        
        // Step 2: Calculate random number based on totalWeight
        int selectedWeight = generator.nextInt() % totalWeight;
        
        // Step 3: Choose the word based on selectedWeight
        iter = collection.iterator();
        int sumWeight = 0;
        Item<T> selected = null;
        while(iter.hasNext()) {
            selected = iter.next();
            sumWeight += selected.weight;
            if(selectedWeight < sumWeight) {
                break;
            }
        }
        return selected.value;
    }
    
    public static <T> T choose(AbstractCollection<Item<T>> collection) {
        return choose(collection, new RandomNumberGenerator());
    }
}

interface NumberGenerator {
    int nextInt();
}

class RandomNumberGenerator implements NumberGenerator {
    Random generator = new Random();
    
    public int nextInt() {
        return generator.nextInt();
    }
}

class FixedNumberGenerator implements NumberGenerator {
    int num;
    
    FixedNumberGenerator(int num) {
        this.num = num;
    }
    
    public int nextInt() {
        return num;
    }
}