private transient @Nullable Node<K, V> tail; // the tail for all keys
  private transient Map<K, KeyList<K, V>> keyToKeyList;
  private transient int size;

  /*
   * Tracks modifications to keyToKeyList so that addition or removal of keys invalidates
   * preexisting iterators. This does *not* track simple additions and removals of values
   * that are not the first to be added or last to be removed for their key.

   * ConcurrentModificationException}, and guarantees to traverse elements as they existed upon
   * construction of the iterator, and may (but is not guaranteed to) reflect any modifications
   * subsequent to construction.
   *
   * @return an iterator over the elements in this queue in proper sequence
   */
  @CanIgnoreReturnValue
  @Override
  public Iterator<E> iterator() {

    /* UnsupportedOperationException on direct modifications. */
    assertThrows(UnsupportedOperationException.class, () -> unmod.put(4, "four"));
    assertThrows(UnsupportedOperationException.class, () -> unmod.forcePut(4, "four"));
    assertThrows(UnsupportedOperationException.class, () -> unmod.putAll(singletonMap(4, "four")));

    /* UnsupportedOperationException on indirect modifications. */

   * elements.length) are all {@code null}.
   */
  @VisibleForTesting transient @Nullable Object @Nullable [] elements;

  /**
   * Keeps track of metadata like the number of hash table bits and modifications of this data
   * structure (to make it possible to throw ConcurrentModificationException in the iterator). Note
   * that we choose not to make this volatile, so we do less of a "best effort" to track such

    </class>
    <!-- Profile support -->
    <class>
      <name>Profile</name>
      <version>1.0.0+</version>
      <superClass>IdentifiableBase</superClass>
      <description>
        Modifications to the build process which is keyed on some sort of environmental parameter.
      </description>
      <fields>
        <field>
          <name>activation</name>
          <version>1.0.0+</version>

   * allocated, the value of {@code metadata} combines the number of bits in the "short hash", in
   * its bottom {@value CompactHashing#HASH_TABLE_BITS_MAX_BITS} bits, with a modification count in
   * the remaining bits that is used to detect concurrent modification during iteration.
   */
  private transient int metadata;

  /** The number of elements contained in the set. */
  private transient int size;

 * an {@code ArrayTable} concurrently and one of the threads modifies its value, there is no
 * guarantee that the new value will be fully visible to the other threads. To guarantee that
 * modifications are visible, synchronize access to the table. Unlike other {@code Table}
 * implementations, synchronization is unnecessary between a thread that writes to one cell and a
 * thread that reads from another.
 *

 * an {@code ArrayTable} concurrently and one of the threads modifies its value, there is no
 * guarantee that the new value will be fully visible to the other threads. To guarantee that
 * modifications are visible, synchronize access to the table. Unlike other {@code Table}
 * implementations, synchronization is unnecessary between a thread that writes to one cell and a
 * thread that reads from another.
 *

        Set<Path> processedPoms = new HashSet<>();
        Set<Path> modifiedPoms = new HashSet<>();
        Set<Path> errorPoms = new HashSet<>();

        try {
            // Phase 1: Write all modifications to temp directory (keeping project structure)
            Path tempDir = createTempProjectStructure(context, pomMap);

            // Phase 2: For each POM, build effective model using the session and analyze plugins

    mod.put(4, "four");
    assertEquals(true, unmod.get(4).equals("four"));
    assertEquals(true, unmod.inverse().get("four").equals(4));

    /* UnsupportedOperationException on direct modifications. */
    assertThrows(UnsupportedOperationException.class, () -> unmod.put(4, "four"));
    assertThrows(UnsupportedOperationException.class, () -> unmod.forcePut(4, "four"));