What data class does Bucket use inside the HashMap implementation in Java?

In the implementation of HashMap in Java, each bucket is represented by a linked list or a tree (starting from Java 8, if there are many elements in a bucket, the list is converted into a red-black tree to improve performance).

Specifically, inside HashMap, a bucket is represented by an object of the class Node<K,V>, which implements the Map.Entry<K,V> interface. Each Node contains a key, a value, a hash, and a reference to the next node in the list:

static class Node<K,V> implements Map.Entry<K,V> {
    final int hash;
    final K key;
    V value;
    Node<K,V> next;
    // ...
}

Thus, a bucket is either null (empty) or a reference to the first Node in the chain, which may lead to other Nodes through the next field.