public ExchangeRate fetch(final Currency source,final Currency target,final Date date){
  final List<Entry> rates=data_.get(hash(source,target));
  final int i=matchValidateAt(rates,date);
  return i == rates.size() - 1 ? rates.get(i).rate : null;
}

public ExchangeRate fetch ( final Currency source , final Currency target , final Date date ) { final List < Entry > rates = data_ . get ( hash ( source , target ) ) ; final int i = matchValidateAt ( rates , date ) ; return i == rates . size ( ) - 1 ? rates . get ( i ) . rate : null ; }
fetches an exchangerate from the hashmap .
