}

  private static final int ENDPOINT = -2;

  /**
   * Contains the link pointers corresponding with the entries, in the range of [0, size()). The
   * high 32 bits of each long is the "prev" pointer, whereas the low 32 bits is the "succ" pointer
   * (pointing to the next entry in the linked list). The pointers in [size(), entries.length) are
   * all "null" (UNSET).
   *

   * equal to each other. If two {@linkplain Object#equals equal} inputs are given to this method,
   * both calls will return the same instance. That is, {@code intern(a).equals(a)} always holds,
   * and {@code intern(a) == intern(b)} if and only if {@code a.equals(b)}. Note that {@code
   * intern(a)} is permitted to return one instance now and a different instance later if the
   * original interned instance was garbage-collected.
   *

    // drop the contract on the method that enforces this queue like behavior since depending on it
    // is likely to be a bug anyway.

    // N.B. All writes to the list and the next pointers must have happened before the above
    // synchronized block, so we can iterate the list without the lock held here.
    RunnableExecutorPair reversedList = null;
    while (list != null) {

   * equal to each other. If two {@linkplain Object#equals equal} inputs are given to this method,
   * both calls will return the same instance. That is, {@code intern(a).equals(a)} always holds,
   * and {@code intern(a) == intern(b)} if and only if {@code a.equals(b)}. Note that {@code
   * intern(a)} is permitted to return one instance now and a different instance later if the
   * original interned instance was garbage-collected.
   *

    Interner<String> pool = Interners.newStrongInterner();
    assertSame(canonical, pool.intern(canonical));
    assertSame(canonical, pool.intern(not));
  }

  public void testStrong_null() {
    Interner<String> pool = Interners.newStrongInterner();
    assertThrows(NullPointerException.class, () -> pool.intern(null));
  }

  public void testStrong_builder() {
    int concurrencyLevel = 42;

    private InternerImpl(MapMaker mapMaker) {
      this.map =
          MapMakerInternalMap.createWithDummyValues(mapMaker.keyEquivalence(Equivalence.equals()));
    }

    @Override
    public E intern(E sample) {
      while (true) {
        // trying to read the canonical...
        @SuppressWarnings("rawtypes") // using raw types to avoid a bug in our nullness checker :(

    private InternerImpl(MapMaker mapMaker) {
      this.map =
          MapMakerInternalMap.createWithDummyValues(mapMaker.keyEquivalence(Equivalence.equals()));
    }

    @Override
    public E intern(E sample) {
      while (true) {
        // trying to read the canonical...
        @SuppressWarnings("rawtypes") // using raw types to avoid a bug in our nullness checker :(

 * RegularImmutableBiMap}, which don't have to recopy the entries created by their {@code Builder}
 * implementations.
 *
 * <p>This base implementation has no key or value pointers, so instances of ImmutableMapEntry (but
 * not its subclasses) can be reused when copied from one ImmutableMap to another.
 *
 * @author Louis Wasserman
 */
@GwtIncompatible // unnecessary