code: public void setFrenchCollation(boolean flag) {
          checkNotFrozen();
          if(flag == isFrenchCollation()) { return; }
          CollationSettings ownedSettings = getOwnedSettings();
          ownedSettings.setFlag(CollationSettings.BACKWARD_SECONDARY, flag);
          setFastLatinOptions(ownedSettings);
      }
docs: Sets the mode for the direction of SECONDARY weights to be used in French collation. The default value is false,
  which treats SECONDARY weights in the order they appear. If set to true, the SECONDARY weights will be sorted
  backwards. See the section on <a href="http://userguide.icu-project.org/collation/architecture">
  French collation</a> for more information.
  
  @param flag
  true to set the French collation on, false to set it off
  @see #isFrenchCollation
  @see #setFrenchCollationDefault