java - 文件编写器无法在 do while 循环中正常工作

Question

如果我在它编译的循环内设置构造函数，但它只写入最后一个输入，我无法将数据写入文件。如果将构造函数放在循环之外，则会出现问题，我无法弄清楚如何解决它。我一直在尝试，但没有任何效果

public static void main(String[] args) throws IOException {
        boolean isRegularClient;
        Scanner myScan = new Scanner (System.in);
        int userChoice;
        File myFile = new File ("invoices.txt");
        try {
            FileWriter myWriter = new FileWriter (myFile);}
        catch (IOException ex) {
            System.out.println("An error occurred.");}
        do{
            System.out.println ("Welcome to Marco's Candy Shop");
            System.out.println ("Our speciality and our unique product is the famous Mysterious Beans.");
            System.out.println ("How many lbs do you want? (only exact amounts)");
            while (!myScan.hasNextInt()){
                myScan.next();
            }
            int quantityCandy = myScan.nextInt();
            System.out.println ("We are giving 20% off to our regular customers. Are you a regular client?");
            String string1 = myScan.next();
            if ("Yes".equals(string1) || "yes".equals(string1)){
                isRegularClient = true;
            }
            else {
                isRegularClient = false;
            }
            System.out.println ("Please Enter your billing adress");
            String adress = myScan.next();
            System.out.println ("How much is your local tax rate? (enter as percent)");
            while (!myScan.hasNextDouble()){
                myScan.next();
            }
            double taxRate = myScan.nextDouble();
            Client newClient = new Client(adress,isRegularClient,quantityCandy,taxRate);
            final double pricexLB = 0.80;
            final double regularClientDiscount = 0.20;
            double orderPrice = (pricexLB * quantityCandy);
            double orderTax = (orderPrice*taxRate)/100;
            double finalCharge;
            if (isRegularClient){
                finalCharge = (orderPrice-(orderPrice*regularClientDiscount))+orderTax;
            }
            else {
                finalCharge = orderPrice+orderTax;
            }
            System.out.println ("You ordered " + quantityCandy + " lbs of the Mysterious Beans. You have to pay " + finalCharge + "$. This invoice will be sent to " + adress);
            try{
                myWriter.write ("You ordered " + quantityCandy + " lbs of the Mysterious Beans. You have to pay " + finalCharge + "$. This invoice will be sent to " + adress);
                myWriter.close();}
            catch (IOException e) {
                System.out.println("An error occurred.");}
            System.out.println ("If you want to make another order please enter 1, otherwise enter any number to exit");
            while (!myScan.hasNextInt()){
            myScan.next();}
            userChoice =  myScan.nextInt();}
        while (1 == userChoice);}
        
        
        
        
    }

标签： java

Answer 1

您以写入模式打开 fileWriter，它通常会清空文件并添加新内容。为此，您必须以附加模式打开文件。

FileWriter 将采用两个参数，第二个参数作为附加模式的布尔值，如果您在 try 块内创建文件写入器，它只能在该范围内访问，您无法在外部访问。所以你也必须在 try/catch 中移动 do/while 块。

try {
         FileWriter myWriter = new FileWriter (myFile, true);
         do{
            System.out.println ("Welcome to Marco's Candy Shop");
            System.out.println ("Our speciality and our unique product is the famous Mysterious Beans.");
            System.out.println ("How many lbs do you want? (only exact amounts)");
            while (!myScan.hasNextInt()){
                myScan.next();
            }
            int quantityCandy = myScan.nextInt();
            System.out.println ("We are giving 20% off to our regular customers. Are you a regular client?");
            String string1 = myScan.next();
            if ("Yes".equals(string1) || "yes".equals(string1)){
                isRegularClient = true;
            }
            else {
                isRegularClient = false;
            }
            System.out.println ("Please Enter your billing adress");
            String adress = myScan.next();
            System.out.println ("How much is your local tax rate? (enter as percent)");
            while (!myScan.hasNextDouble()){
                myScan.next();
            }
            double taxRate = myScan.nextDouble();
            Client newClient = new Client(adress,isRegularClient,quantityCandy,taxRate);
            final double pricexLB = 0.80;
            final double regularClientDiscount = 0.20;
            double orderPrice = (pricexLB * quantityCandy);
            double orderTax = (orderPrice*taxRate)/100;
            double finalCharge;
            if (isRegularClient){
                finalCharge = (orderPrice-(orderPrice*regularClientDiscount))+orderTax;
            }
            else {
                finalCharge = orderPrice+orderTax;
            }
            System.out.println ("You ordered " + quantityCandy + " lbs of the Mysterious Beans. You have to pay " + finalCharge + "$. This invoice will be sent to " + adress);
            try{
                myWriter.write ("You ordered " + quantityCandy + " lbs of the Mysterious Beans. You have to pay " + finalCharge + "$. This invoice will be sent to " + adress);
                myWriter.close();}
            catch (IOException e) {
                System.out.println("An error occurred.");}
            System.out.println ("If you want to make another order please enter 1, otherwise enter any number to exit");
            while (!myScan.hasNextInt()){
            myScan.next();}
            userChoice =  myScan.nextInt();}
        while (1 == userChoice);}
} catch (IOException ex) {
            System.out.println("An error occurred.");
}

请参阅此文档以获取更多信息。