public StockPriceProvider() {
        Share[] buffershare = new Share[0];
        if(this instanceof YahooFinancePriceProvider){
            buffershare = createShares();
        }else if(this instanceof HistoricalStockPriceProvider){
            buffershare = createDefaulShares();
        }
    	
    	for (int i = 0; i < buffershare.length; i++) {
			availableShare.add(buffershare[i]);
		}
        Comparator<Share> comperator = new ShareComparator();
        Collections.sort(this.availableShare, comperator);
        startUpdate();
    }