// Re-declare this as abstract to force subclasses to override.
  @Override
  public abstract String toString();

  public static CommonPattern compile(String pattern) {
    return Platform.compilePattern(pattern);
  }

  public static boolean isPcreLike() {
    return Platform.patternCompilerIsPcreLike();
  }

  // Re-declare this as abstract to force subclasses to override.
  @Override
  public abstract String toString();

  public static CommonPattern compile(String pattern) {
    return Platform.compilePattern(pattern);
  }

  public static boolean isPcreLike() {
    return Platform.patternCompilerIsPcreLike();
  }

    return string || "";
  }-*/;

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

  static CommonPattern compilePattern(String pattern) {
    throw new UnsupportedOperationException();
  }

  static boolean patternCompilerIsPcreLike() {
    throw new UnsupportedOperationException();
  }

  private Platform() {}

   */
  @CheckForNull
  static String emptyToNull(@CheckForNull String string) {
    return stringIsNullOrEmpty(string) ? null : string;
  }

  static CommonPattern compilePattern(String pattern) {
    Preconditions.checkNotNull(pattern);
    return patternCompiler.compile(pattern);
  }

  static boolean patternCompilerIsPcreLike() {
    return patternCompiler.isPcreLike();
  }

   *     malformed expression
   */
  @GwtIncompatible // java.util.regex
  public static Splitter onPattern(String separatorPattern) {
    return onPatternInternal(Platform.compilePattern(separatorPattern));
  }

  /**
   * Returns a splitter that divides strings into pieces of the given length. For example, {@code