public class HashMap<K, V> {

    private final int bucketCount = 16;
    private final Bucket<K, V>[] buckets = new Bucket[bucketCount];
    private int size = 0;

    private int getBucketIndex(K key) {
        return key.hashCode() & (bucketCount - 1);
    }

    public void put(K key, V value) {
        int bucketIndex = getBucketIndex(key);

        Bucket<K, V> bucket = buckets[bucketIndex];

        if (bucket == null) {
            bucket = new Bucket<>();
            buckets[bucketIndex] = bucket;
        }

        bucket.put(key, value);
        size++;
    }

    public V get(K key) {
        int bucketIndex = getBucketIndex(key);

        Bucket<K, V> bucket = buckets[bucketIndex];

        if (bucket == null) {
            return null;
        }

        return bucket.get(key);
    }

    public void remove(K key) {
        int bucketIndex = getBucketIndex(key);

        Bucket<K, V> bucket = buckets[bucketIndex];

        if (bucket == null) {
            return;
        }

        bucket.remove(key);
        size--;
    }

    public int size() {
        return size;
    }

}