public void saveLater(){
  if (savePending.getAndSet(true))   return;
  executor.schedule(saver,delay,delayTimeUnit);
}

public void saveLater ( ) { if ( savePending . getAndSet ( true ) ) return ; executor . schedule ( saver , delay , delayTimeUnit ) ; }
queues up a save in the background . useful for not very important wallet changes .
