code: public final void setCaseFirstDefault() {
          checkNotFrozen();
          CollationSettings defaultSettings = getDefaultSettings();
          if(settings.readOnly() == defaultSettings) { return; }
          CollationSettings ownedSettings = getOwnedSettings();
          ownedSettings.setCaseFirstDefault(defaultSettings.options);
          setFastLatinOptions(ownedSettings);
      }
docs: Sets the case first mode to the initial mode set during construction of the RuleBasedCollator. See
  setUpperCaseFirst(boolean) and setLowerCaseFirst(boolean) for more details.
  
  @see #isLowerCaseFirst
  @see #isUpperCaseFirst
  @see #setLowerCaseFirst(boolean)
  @see #setUpperCaseFirst(boolean)