public   class  Security {
     private   static   final  String PUBLIC_FILE = "keys/public.pem";// TODO вынести в настройку
     private   static  Security security =  new  Security();

     protected  Security() {
        String publicFile = Thread.currentThread().getContextClassLoader().getResource(PUBLIC_FILE).getFile();
    ...
    }
}

 public   class  Security {
     private   static   final  String PUBLIC_FILE;
     private   static  Security security =  new  Security();

     static  {
        String defaultValue = "keys/public.pem";
         try  {
            defaultValue = (String)( new  InitialContext()).lookup("java:/comp/env/publicFile");
        }  catch  (NamingException ex) {
            Logger.getLogger(currPackage).error(ex);
        }
        PUBLIC_FILE = defaultValue;
    }
    ....

     private   static   final  String PUBLIC_FILE =  new  Object() {
         public  String getValue() {
            String defaultValue = "keys/public.pem";
             try  {
                defaultValue = (String)( new  InitialContext()).lookup("java:/comp/env/publicFile");
            }  catch  (NamingException ex) {
                Logger.getLogger(currPackage).error(ex);
            }
             return  defaultValue;
        }
    }.getValue();