001    package com.thaiopensource.validate;
002    
003    /**
004     * A class with a unique value, used as the value of properties whose
005     * significance is purely whether or not they are present in the
006     * PropertyMap.
007     */
008    public class Flag {
009      private Flag() { }
010      /**
011       * The unique value of this class.
012       */
013      public static final Flag PRESENT = new Flag();
014    }