}
        }
    }

    /**
     * Concatenates kind arrays, avoiding duplicates.
     * @param kinds The initial kind array.
     * @param newKinds The new kind array to add.
     * @return The concatenated kind array.
     */
    protected static Kind[] concatKinds(final Kind[] kinds, final Kind... newKinds) {
        if (kinds == null) {
            return newKinds;
        }

    /** The document frequency field. */
    public static final String DOC_FREQ = "docFreq";
    /** The user boost field. */
    public static final String USER_BOOST = "userBoost";
    /** The kinds field. */
    public static final String KINDS = "kinds";
    /** The timestamp field. */
    public static final String TIMESTAMP = "@timestamp";
    /** The tags field. */
    public static final String TAGS = "tags";
    /** The roles field. */

    @Test
    public void testConcatKinds() {
        // Test static concatKinds method
        SuggestItem.Kind[] kinds1 = { SuggestItem.Kind.QUERY };
        SuggestItem.Kind[] kinds2 = { SuggestItem.Kind.DOCUMENT, SuggestItem.Kind.QUERY };

        SuggestItem.Kind[] result = SuggestItem.concatKinds(kinds1, kinds2);

        assertNotNull(result);
        assertEquals(2, result.length); // Should not have duplicates

        return deleteWordsByKind(index, FieldNames.QUERY_FREQ, SuggestItem.Kind.QUERY, item -> item.setQueryFreq(0),
                SuggestItem.Kind.DOCUMENT, SuggestItem.Kind.USER);
    }

    /**
     * Common method to delete words by kind.
     *
     * @param index The index name
     * @param freqField The frequency field name
     * @param kindToRemove The kind to remove
     * @param freqSetter The consumer to set frequency to 0

    }

    /**
     * Merges two Kind arrays, maintaining uniqueness.
     */
    private static SuggestItem.Kind[] mergeKinds(final SuggestItem.Kind[] kinds1, final SuggestItem.Kind[] kinds2) {
        final Set<SuggestItem.Kind> merged = new LinkedHashSet<>();

        if (kinds1 != null) {
            Collections.addAll(merged, kinds1);
        }

        if (kinds2 != null) {

-->

#### What type of PR is this?

<!--
Add one of the following kinds:
/kind bug
/kind dependency
/kind cleanup
/kind documentation
/kind feature

Optionally add one or more of the following kinds if applicable:
/kind api-change
/kind deprecation
/kind failing-test
/kind flake
/kind regression
-->

#### What this PR does / why we need it:

     */
    public void addField(final String field) {
        fields.add(field);
    }

    /**
     * Adds a kind to filter by.
     * @param kind The kind.
     */
    public void addKind(final String kind) {
        kinds.add(kind);
    }

    /**
     * Sets whether to return detailed suggestion information.

### SuggestItem (Domain Entity)
Location: `src/main/java/org/codelibs/fess/suggest/entity/SuggestItem.java`

Core attributes: `text`, `timestamp`, `queryFreq`, `docFreq`, `userBoost`, `readings`, `tags`, `roles`, `languages`, `kinds`

Kind types: `DOCUMENT`, `QUERY`, `USER`

---

## Development Workflow

### Build Commands

```bash
mvn compile                              # Compile

    extends AbstractFuture<V> {
  /*
   * In the GWT versions of the methods (below), every exceptionType parameter is required to be
   * Class<Throwable>. To handle only certain kinds of exceptions under GWT, you'll need to write
   * your own instanceof tests.
   */

  public final FluentFuture<V> catching(
      Class<Throwable> exceptionType,
      Function<? super Throwable, ? extends V> fallback,

 */
abstract class GwtFuturesCatchingSpecialization {
  /*
   * In the GWT versions of the methods (below), every exceptionType parameter is required to be
   * Class<Throwable>. To handle only certain kinds of exceptions under GWT, you'll need to write
   * your own instanceof tests.
   */

  public static <V extends @Nullable Object> ListenableFuture<V> catching(
      ListenableFuture<? extends V> input,