初始化和FileNotFoundException错误

Question

我是一个新的Java学生，正在编写一个程序，它由一个main方法，一个类文件，两个input.txt文件和一个output.txt文件组成。主要方法应该询问用户帐户余额和年息是多少，并从它们各自的文件中导入存款和取款信息，然后在输出文件中显示来自类文件的所有计算。我最初写这个文件是为了要求用户使用扫描仪输入所有这些信息，现在我正在尝试使用文件作为输入来让它工作……这并不是很顺利。

主要方法：

    import java.util.Scanner;
    import java.io.*;
    public class SavingsAccountDemo {

   public static void main(String[] args) {
   //declare variables
   double interest;
   double startAmount;
   double amountDeposit;
   double amountWithdraw;
   double d, w;
   String filenameInputW, filenameInputD, filenameOutput;
   PrintWriter oFile;
   File wFile, dFile;
   Scanner iFile;

   Scanner key = new Scanner(System.in);

    //get initial balance
   System.out.println("Enter initial account balance: ");
   startAmount = key.nextDouble();

   //create SavingsAccount class object sending starting amount to constructor
   SavingsAccount money = new SavingsAccount(startAmount);

   //get annual interest rate
   System.out.println("Enter annual interest rate: ");
   interest = key.nextDouble();

   //send interest rate to class
   money.setInterest(interest);

   //Retrieve withdrawals from withdrawal.txt
   filenameInputW="withdrawal.txt";
   wFile = new File (filenameInputW);
   iFile = new Scanner (wFile);
   while(iFile.hasNext())
   {
        double num;

        num=iFile.nextDouble();
        amountWithdraw += num;

        if(amountWithdraw >= 0.1)
        w++;
   }

   //send to SavingsAccount class
    money.withdraw(amountWithdraw);

   //Retrieve deposits from deposit.txt
   filenameInputD="deposit.txt";
   dFile = new File (filenameInputD);
   iFile = new Scanner (dFile);

   while(iFile.hasNext())
   {
        double num;

        num=iFile.nextDouble();
        amountDeposit += num;

        if (amountDeposit >= 0.1)
        d++;
   }

   //send to SavingsAccount class
    money.deposit(amountDeposit);

   //display retults
   filenameInputW="output.txt";
   oFile=new PrintWriter (filenameOutput);
   oFile.println("The ending balance is: " + money.getBalance());
   oFile.println("The total amount of withdrawls are: " + w);
   oFile.println("The total amount of deposists are: " + d);
   oFile.println("The annual interest rate is: " + money.getInterest());

}

}

我的类文件

/**
 * @(#)SavingsAccount.java
 *
 *
 * @author 
 * @version 1.00 2013/5/6
 */


public class SavingsAccount {

        //variables
        private double interest;
        private double balance;


        //Constructor
        public SavingsAccount(double b)
        {
            balance = b;
            interest = 0.0;
        }

        //Accessors
        public void setInterest(double i)
        {
            interest = i;
        }

        public void setBalance(double b)
        {
            balance = b;
        }

        //Mutators
        public double getInterest()
        {
            return interest;
        }

        public double getBalance()
        {
            return balance;
        }

        //Withdraw method
        public void withdraw(double withdraw)
        {
            balance = balance - withdraw;
        }

        //Deposit method
        public void deposit(double deposit)
        {
            balance = balance + deposit;
        }


        //Adding monthly interest to the balance
        public void addInterest()
        {
            double x = ((interest/12) * balance);
            balance = balance + x;
        }

}

我得到了这些错误：

--------------------Configuration: --------------------
C:\Users\Home\Documents\JCreator Pro\MyProjects\SavingsAccount\src\SavingsAccountDemo.java:43: error: variable amountWithdraw might not have been initialized
            amountWithdraw += num;
            ^
C:\Users\Home\Documents\JCreator Pro\MyProjects\SavingsAccount\src\SavingsAccountDemo.java:46: error: variable w might not have been initialized
            w++;
            ^
C:\Users\Home\Documents\JCreator Pro\MyProjects\SavingsAccount\src\SavingsAccountDemo.java:50: error: variable amountWithdraw might not have been initialized
        money.withdraw(amountWithdraw);
                       ^
C:\Users\Home\Documents\JCreator Pro\MyProjects\SavingsAccount\src\SavingsAccountDemo.java:62: error: variable amountDeposit might not have been initialized
            amountDeposit += num;
            ^
C:\Users\Home\Documents\JCreator Pro\MyProjects\SavingsAccount\src\SavingsAccountDemo.java:65: error: variable d might not have been initialized
            d++;
            ^
C:\Users\Home\Documents\JCreator Pro\MyProjects\SavingsAccount\src\SavingsAccountDemo.java:69: error: variable amountDeposit might not have been initialized
        money.deposit(amountDeposit);
                      ^
C:\Users\Home\Documents\JCreator Pro\MyProjects\SavingsAccount\src\SavingsAccountDemo.java:73: error: variable filenameOutput might not have been initialized
       oFile=new PrintWriter (filenameOutput);
                              ^
C:\Users\Home\Documents\JCreator Pro\MyProjects\SavingsAccount\src\SavingsAccountDemo.java:75: error: variable w might not have been initialized
       oFile.println("The total amount of withdrawls are: " + w);
                                                              ^
C:\Users\Home\Documents\JCreator Pro\MyProjects\SavingsAccount\src\SavingsAccountDemo.java:76: error: variable d might not have been initialized
       oFile.println("The total amount of deposists are: " + d);
                                                             ^
C:\Users\Home\Documents\JCreator Pro\MyProjects\SavingsAccount\src\SavingsAccountDemo.java:37: error: unreported exception FileNotFoundException; must be caught or declared to be thrown
       iFile = new Scanner (wFile);
               ^
C:\Users\Home\Documents\JCreator Pro\MyProjects\SavingsAccount\src\SavingsAccountDemo.java:55: error: unreported exception FileNotFoundException; must be caught or declared to be thrown
       iFile = new Scanner (dFile);
               ^
C:\Users\Home\Documents\JCreator Pro\MyProjects\SavingsAccount\src\SavingsAccountDemo.java:73: error: unreported exception FileNotFoundException; must be caught or declared to be thrown
       oFile=new PrintWriter (filenameOutput);
             ^
12 errors

Process completed.

我不是在找施舍，这是我的第一个帖子在这里寻求帮助，但我知道你们不会为我解决这个...我只是需要学习如何做到这一点正确。我只是不知道为什么初始化有问题（所有提到的变量都是初始化的）和文件位于同一个文件夹。

Answer 1

我想您对初始化和声明之间的区别感到困惑。给出错误的变量确实声明了，但它们没有初始值。

看看w++。这意味着：将1添加到w。但是什么是w？你没给出定义。

对于D、AmountithDraw和AmountDestory也存在同样的问题

此外，使用文件作为输入的新扫描器需要FileNotFoundException的try-catch语句。

最后，我想您的意思是filenameoutput=“output.txt”；而不是filenameinputw=“output.txt”；