Is HashMap internally implemented in Java using LinkedList or Array?

Question

How is HashMap internally implemented? I read somewhere that it uses LinkedList while other places it mentions Arrays.

I tried studying the

Answer 1

HashMap has an array of HashMap.Entry objects :

/**
 * The table, resized as necessary. Length MUST Always be a power of two.
 */
transient Entry[] table; 

We can say that Entry is a one-way linked list (such HashMap.Entry linkage is called "Bucket") but it is not actually a java.util.LinkedList.

See for yourself :

static class Entry implements Map.Entry {
        final K key;
        V value;
        Entry next;
        int hash;

        /**
         * Creates new entry.
         */
        Entry(int h, K k, V v, Entry n) {
            value = v;
            next = n;
            key = k;
            hash = h;
        }

        public final K getKey() {
            return key;
        }

        public final V getValue() {
            return value;
        }

        public final V setValue(V newValue) {
            V oldValue = value;
            value = newValue;
            return oldValue;
        }

        public final boolean equals(Object o) {
            if (!(o instanceof Map.Entry))
                return false;
            Map.Entry e = (Map.Entry)o;
            Object k1 = getKey();
            Object k2 = e.getKey();
            if (k1 == k2 || (k1 != null && k1.equals(k2))) {
                Object v1 = getValue();
                Object v2 = e.getValue();
                if (v1 == v2 || (v1 != null && v1.equals(v2)))
                    return true;
            }
            return false;
        }

        public final int hashCode() {
            return (key==null   ? 0 : key.hashCode()) ^
                   (value==null ? 0 : value.hashCode());
        }

        public final String toString() {
            return getKey() + "=" + getValue();
        }

        /**
         * This method is invoked whenever the value in an entry is
         * overwritten by an invocation of put(k,v) for a key k that's already
         * in the HashMap.
         */
        void recordAccess(HashMap m) {
        }

        /**
         * This method is invoked whenever the entry is
         * removed from the table.
         */
        void recordRemoval(HashMap m) {
        }
    }