* Preconditions} class use this formatter, for both of the reasons just discussed.
   *
   * <p><b>Warning:</b> Only the exact two-character placeholder sequence {@code "%s"} is
   * recognized.
   *
   * @param template a string containing zero or more {@code "%s"} placeholder sequences. {@code
   *     null} is treated as the four-character string {@code "null"}.

    return (Collector) TO_OPTIONAL;
  }

  private static final Object NULL_PLACEHOLDER = new Object();

  private static final Collector<@Nullable Object, ?, @Nullable Object> ONLY_ELEMENT =
      Collector.<@Nullable Object, ToOptionalState, @Nullable Object>of(
          ToOptionalState::new,
          (state, o) -> state.add((o == null) ? NULL_PLACEHOLDER : o),
          ToOptionalState::combine,
          state -> {

   * Preconditions} class use this formatter, for both of the reasons just discussed.
   *
   * <p><b>Warning:</b> Only the exact two-character placeholder sequence {@code "%s"} is
   * recognized.
   *
   * @param template a string containing zero or more {@code "%s"} placeholder sequences. {@code
   *     null} is treated as the four-character string {@code "null"}.

import java.util.Locale;

/**
 * This class is emulated in GWT.
 *
 * @author Hayward Chan
 */
@GwtCompatible
final class Platform {

  /** Format the template with args, only supports the placeholder {@code %s}. */
  static String format(String template, Object... args) {
    return String.format(Locale.ROOT, template, args);
  }

  /** See {@link ListListIteratorTester} */

import java.util.Locale;

/**
 * This class is emulated in GWT.
 *
 * @author Hayward Chan
 */
@GwtCompatible
final class Platform {

  /** Format the template with args, only supports the placeholder {@code %s}. */
  static String format(String template, Object... args) {
    return String.format(Locale.ROOT, template, args);
  }

  /** See {@link ListListIteratorTester} */

  - type: textarea
    attributes:
      label: API(s)
      description: Which existing classes or methods do you want to improve?
      placeholder: e.g., `com.google.common.collect.ImmutableList::of`
      render: java
    validations:
      required: true

  - type: textarea
    attributes:
      label: How do you want it to be improved?
    validations:

   *     message is formed by replacing each {@code %s} placeholder in the template with an
   *     argument. These are matched by position - the first {@code %s} gets {@code
   *     errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted message in
   *     square braces. Unmatched placeholders will be left as-is.

        in flux. This can make the feature you're suggesting much clearer to us.

  - type: textarea
    attributes:
      label: (Optional) What would the method signatures for your feature look like?
      placeholder: |
        e.g.,
        public static <E> ImmutableList<E> of();
        public static <E> ImmutableList<E> of(E element);
        public static <E> ImmutableList<E> of(E e1, E e2);
        ...
      render: java

   *     message is formed by replacing each {@code %s} placeholder in the template with an
   *     argument. These are matched by position - the first {@code %s} gets {@code
   *     errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted message in
   *     square braces. Unmatched placeholders will be left as-is.

   *     message is formed by replacing each {@code %s} placeholder in the template with an
   *     argument. These are matched by position - the first {@code %s} gets {@code
   *     errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted message in
   *     square braces. Unmatched placeholders will be left as-is.