Time Complexity of HashMap methods

Question

Since i\'m working around time complexity, i\'ve been searching through the oracle Java class library for the time complexity of some standard methods used on Lists, Maps an

Answer 1

The code for remove(as in rt.jar for HashMap) is:

/**
 * Removes and returns the entry associated with the specified key
 * in the HashMap.  Returns null if the HashMap contains no mapping
 * for this key.
 */
final Entry removeEntryForKey(Object key) {
    int hash = (key == null) ? 0 : hash(key.hashCode());
    int i = indexFor(hash, table.length);
    Entry prev = table[i];
    Entry e = prev;

    while (e != null) {
        Entry next = e.next;
        Object k;
        if (e.hash == hash &&
            ((k = e.key) == key || (key != null && key.equals(k)))) {
            modCount++;
            size--;
            if (prev == e)
                table[i] = next;
            else
                prev.next = next;
            e.recordRemoval(this);
            return e;
        }
        prev = e;
        e = next;
    }

    return e;
}

Clearly, the worst case is O(n).