// It's possible to keep using this Builder after calling buildKeepingLast(), so we need to
      // ensure that its state is not corrupted by removing duplicates that should cause a later
      // buildOrThrow() to fail, or by changing the size.
      @Nullable Entry<K, V>[] localEntries;
      int localSize = size;
      if (valueComparator == null) {
        localEntries = entries;
      } else {

    @Nullable Object[] alternatingKeysAndValues;
    int size;
    boolean entriesUsed;
    /**
     * If non-null, a duplicate key we found in a previous buildKeepingLast() or buildOrThrow()
     * call. A later buildOrThrow() can simply report this duplicate immediately.
     */
    @Nullable DuplicateKey duplicateKey;

    /**
     * Creates a new builder. The returned builder is equivalent to the builder generated by {@link