code: @Deprecated
      public String getRegexEquivalent() {
          if (strings.size() == 0) {
              return toString();
          }
          StringBuilder result = new StringBuilder("(?:");
          appendNewPattern(result, true, false);
          for (String s : strings) {
              result.append('|');
              _appendToPat(result, s, true);
          }
          return result.append(")").toString();
      }
docs: Get the Regex equivalent for this UnicodeSet
  @return regex pattern equivalent to this UnicodeSet
  @deprecated This API is ICU internal only.
  @hide original deprecated declaration
  @hide draft / provisional / internal are hidden on Android