public static String double2String(Double d){
        return d==null? "0.00" : String.format("%.2f", d);
    }

在報文前邊加8位長度

public String dealMessageBeforeWriting(String reqMsg)  {

        String length = "";
        try {
            length = String.format("%1$08d", reqMsg.getBytes("UTF-8").length);
        } catch
 
 (UnsupportedEncodingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        reqMsg = length + reqMsg;

        return reqMsg;
    }