private int index = -1;
        private final int maxIndex = keyToIndex().size();

        @Override
        protected @Nullable Entry<K, V> computeNext() {
          for (index++; index < maxIndex; index++) {
            V value = getValue(index);
            if (value != null) {
              return immutableEntry(getKey(index), value);
            }
          }

            if (logger.isDebugEnabled()) {
                logger.debug("Failed to create suggest index: index={}", index, e);
            }
            throw new SuggesterException("Failed to create suggest index: " + index, e);
        }
    }

    /**
     * Creates a new index and replaces the current update alias with the new index.
     */
    public void createNextIndex() {
        try {

          S extends MapWithIndexSpliterator<F, R, S>>
      implements Spliterator<R> {
    final F fromSpliterator;
    long index;

    MapWithIndexSpliterator(F fromSpliterator, long index) {
      this.fromSpliterator = fromSpliterator;
      this.index = index;
    }

    abstract S createSplit(F from, long i);

    @Override
    public @Nullable S trySplit() {

Location: `src/main/java/org/codelibs/fess/suggest/Suggester.java`

Main operations: `suggest()`, `popularWords()`, `indexer()`, `createIndexIfNothing()`, `createNextIndex()`, `switchIndex()`, `removeDisableIndices()`

### SuggestIndexer (Indexing Engine)
Location: `src/main/java/org/codelibs/fess/suggest/index/SuggestIndexer.java`

Handles all indexing operations, content parsing, and word management (bad words, elevate words).

 * transforms them into indexed documents, and updates the OpenSearch index.
 *
 * <p>The updater performs the following key operations:
 * <ul>
 * <li>Retrieves crawled documents from the data service</li>
 * <li>Transforms document data using appropriate transformers</li>
 * <li>Applies document boosting rules and click/favorite count enhancements</li>
 * <li>Sends processed documents to the search engine for indexing</li>

  /**
   * Returns the {@code int} value present at the given index.
   *
   * @throws IndexOutOfBoundsException if {@code index} is negative, or greater than or equal to
   *     {@link #length}
   */
  public int get(int index) {
    Preconditions.checkElementIndex(index, length());
    return array[start + index];
  }

  /**
   * Returns the smallest index for which {@link #get} returns {@code target}, or {@code -1} if no

  /**
   * Returns the {@code long} value present at the given index.
   *
   * @throws IndexOutOfBoundsException if {@code index} is negative, or greater than or equal to
   *     {@link #length}
   */
  public long get(int index) {
    Preconditions.checkElementIndex(index, length());
    return array[start + index];
  }

  /**
   * Returns the smallest index for which {@link #get} returns {@code target}, or {@code -1} if no

    protected volatile long executeTime = 0;

    /** List of documents waiting to be indexed */
    protected final DocList docList = new DocList();

    /** Maximum size of document requests in bytes */
    protected long maxDocumentRequestSize;

    /** Maximum number of documents to cache before indexing */
    protected int maxDocumentCacheSize;

    /** Factory for creating ingesters to process documents */

  }

  @Override
  public @Nullable V get(@Nullable Object key) {
    Map<K, V> delegate = delegateOrNull();
    if (delegate != null) {
      return delegate.get(key);
    }
    int index = indexOf(key);
    if (index == -1) {
      return null;
    }
    accessEntry(index);
    return value(index);
  }

  @CanIgnoreReturnValue

import org.codelibs.fess.util.ComponentUtil;

/**
 * Helper class for web and file system crawling and indexing operations.
 * Manages the crawling process for both web configurations and file configurations,
 * coordinating multiple crawler threads and handling indexing operations.
 */
public class WebFsIndexHelper {

    /**
     * Default constructor.
     */
    public WebFsIndexHelper() {