// already using Collections.newSetFromMap and ConcurrentHashMap.
    return Collections.newSetFromMap(new ConcurrentHashMap<E, Boolean>());
  }

  static <E> Set<E> newLinkedHashSetWithExpectedSize(int expectedSize) {
    return Sets.newLinkedHashSetWithExpectedSize(expectedSize);
  }

  /**
   * Returns the platform preferred map implementation that preserves insertion order when used only
   * for insertions.

 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
final class Platform {
  private Platform() {}

  /** Returns a thread-local 1024-char array. */
  static char[] charBufferFromThreadLocal() {
    // requireNonNull accommodates Android's @RecentlyNullable annotation on ThreadLocal.get
    return requireNonNull(DEST_TL.get());
  }

  /**

    return Maps.newLinkedHashMapWithExpectedSize(expectedSize);
  }

  /** Returns the platform preferred implementation of a set based on a hash table. */
  static <E extends @Nullable Object> Set<E> newHashSetWithExpectedSize(int expectedSize) {
    return Sets.newHashSetWithExpectedSize(expectedSize);
  }

  /** Returns the platform preferred implementation of a thread-safe hash set. */

    return CompactLinkedHashMap.createWithExpectedSize(expectedSize);
  }

  /** Returns the platform preferred implementation of a set based on a hash table. */
  static <E extends @Nullable Object> Set<E> newHashSetWithExpectedSize(int expectedSize) {
    return CompactHashSet.createWithExpectedSize(expectedSize);
  }

  /**

   * @param string the string to test and possibly return
   * @return {@code string} if it is not null; {@code ""} otherwise
   */
  static String nullToEmpty(@CheckForNull String string) {
    return (string == null) ? "" : string;
  }

  /**
   * Returns the string if it is not empty, or a null string otherwise.
   *
   * @param string the string to test and possibly return

   * @param string the string to test and possibly return
   * @return {@code string} if it is not null; {@code ""} otherwise
   */
  static String nullToEmpty(@CheckForNull String string) {
    return (string == null) ? "" : string;
  }

  /**
   * Returns the string if it is not empty, or a null string otherwise.
   *
   * @param string the string to test and possibly return

  @JsMethod
  static native boolean stringIsNullOrEmpty(@Nullable String string) /*-{
    return !string;
  }-*/;

  @JsMethod
  static native String nullToEmpty(@Nullable String string) /*-{
    return string || "";
  }-*/;

  @JsMethod
  static native String emptyToNull(@Nullable String string) /*-{
    return string || null;
  }-*/;

  static CommonPattern compilePattern(String pattern) {