RandomBucket

public final class RandomBucket
{
    private final Random random;
    private final int min;
    private final int max;
    private final List<Integer> bucket;

    public RandomBucket(final int max)
    {
        this(0, max);
    }

    public RandomBucket(final int min, final int max)
    {
        this.random = new Random();
        this.min = min;
        this.max = max;
        this.bucket = new ArrayList<Integer>();

        this.fillIfNeeded();
    }

    private void fillIfNeeded()
    {
        if (this.bucket.size() != 0)
            return;

        for (int i = this.min; i < this.max; i++)
            this.bucket.add(i);
    }

    public int next()
    {
        this.fillIfNeeded();

        final int index = this.random.nextInt(this.bucket.size());
        return this.bucket.remove(index);
    }
}