private void setFieldSequenceInTradeFile(String header) {
        String token;
        String tradeId = "Trade_id";
        String sellerAcct = "Seller_acct";
        String buyerAcct = "Buyer_acct";
        String amount = "Amount";
        String tradeDate = "Trade_date";
        String settledDate = "Settled_date";
        StringTokenizer st = new StringTokenizer(header, ",");

        for (int i = 0; i < 6; i++) {
            token = st.nextToken();
            if (token.equals(tradeId)) {
                fieldSequenceInTradeFile.put(tradeId, i);
                continue;
            }
            if (token.equals(sellerAcct)) {
                fieldSequenceInTradeFile.put(sellerAcct, i);
                continue;
            }
            if (token.equals(buyerAcct)) {
                fieldSequenceInTradeFile.put(buyerAcct, i);
                continue;
            }
            if (token.equals(amount)) {
                fieldSequenceInTradeFile.put(amount, i);
                continue;
            }
            if (token.equals(tradeDate)) {
                fieldSequenceInTradeFile.put(tradeDate, i);
                continue;
            }
            if (token.equals(settledDate)) {
                fieldSequenceInTradeFile.put(settledDate, i);
            }
        }
        if (fieldSequenceInTradeFile.isEmpty()) {
            System.out.println("an error occurred during parsing file header! file name: " +
                    shortTradeFileName);
        }
    }