Java 数字格式中的空字符串

我的任务是：

以下是我的问题：

如何修复此错误：

线程“main”java.lang.NumberFormatException中的异常：空字符串 在sun.misc.FloatingDecimal.readJavaFormatString（FloatingDecimal.java:1012）中 在java.lang.Double.parseDouble（Double.java:527） 位于extracredit.Main.readData（Main.java:72） 位于extracredit.Main.Main（Main.java:27）

这个程序还有其他问题吗

以下是我目前的代码：

    import java.io.*;
            import javax.swing.JOptionPane;
            import java.util.*;
            import java.util.StringTokenizer;

            public class Main {
     public static void main(String[] args) throws IOException {
     String fname = "data.txt"; //Read in the data file for use in the array
     String pass= JOptionPane.showInputDialog("Please enter the " +
             "password to continue:"); /*Have the user enter the password to 
     access the file. */

     checkPass(pass); // Verify that the password is correct before continuing.
     readData (fname); // Read data, print output and save output file.

  }


    private static void checkPass (String pass)
    {
     String password= "INF260";
     int passCount= 0;   
       if (pass.equals(password)) {
         System.out.println("The password is correct. Continuing...");
       }
       else {
        do {
           pass= JOptionPane.showInputDialog("Please re-enter the" +
                   "password:");
           passCount++;
        } while (!pass.equals(password) && passCount < 2);
           if (!pass.equals(password)) {
            System.out.println("You have tried to enter the " +
                   "password too many times. Exiting...");
            System.exit(0);
           }
           else {
               System.out.println("The password is correct. Continuing...");
           }
       }
    }
       public static void readData (String data) throws IOException{           
            FileReader inputData= new FileReader (data);
            BufferedReader findNum= new BufferedReader (inputData);
            String str= findNum.readLine ();

            int count=-1;
            int countNum= 0; 
            double total= 0;
            double min= 0;
            double max= 0;
            double average= 0;

            FileWriter writeFile = new FileWriter("sales.txt");
            PrintWriter printFile = new PrintWriter(writeFile);

            while (str != null)
             {
             double num= Double.parseDouble (str);
             if (count == 0){
               countNum++; // counter of Reciepts to use
              }
            str = findNum.readLine();
        }
           double [][] input = new double [countNum][10];
            total= getCurrentTotal(input); /*This will get the total 
             from the method getCurrentTotal.*/
            min= getCurrentMin(input); /*This will get the minimum value from
            the method getCurrentMin.*/
            max= getCurrentMax (input);  /*This will get the maximum value from
            the method getCurrentMax.*/

            average= (total / countNum);   //Calculate the average.     
            System.out.println("The List of Today's Sales:");
                for (int row = 0; row < input.length; row++){
                    System.out.println ();
                    System.out.println("Customer " + row + "\t");
                    for (int column = 0; column < input[row].length; column++){
                       if (input [row].length < 10){        
                        System.out.println(input[row][column] + "\t");
                        str = findNum.readLine();
                    }              
                    else{ 
                        System.out.println ("There are too many receipts" +
                                " for one Customer.\n");
                        System.exit (0);
                    }
                }

            }

    System.out.println ("There are " + countNum + "receipts in the list."); 
        /*This will print the total of receipts in the list.*/                      
    System.out.println ("The total of today's sales is $" + total); /*
        This will print the total of the sales for the day.*/
    System.out.println ("The average of today's sales is $" + average); /*  
        This will print the average sale total.*/
    System.out.println ("The highest receipt is $" + max); /* This will print 
         the highest sale.*/
    System.out.println ("The lowest receipt is $" + min); /* This will print 
        the lowest sale.*/
    Date date = new Date();
        System.out.println ("\n The current time is:" + date.toString()); /* This 
         will print the current date and time */

       }



    public static double getCurrentTotal (double [][] input){
        double totalAmount = 0;
        for (int row = 0; row < input.length; row++){
            for (int column = 0; column < input [row].length; column++){
                totalAmount += input [row][column];
            }
        }
        return totalAmount;    
    }

    public static double getCurrentMin (double [][] input) {    
        double currentMin = input[0][0]; 
        for (int row = 0; row < input.length; row++){
            for (int column = 0; column < input [row].length; column++){
                if (currentMin > input[row][column])
                    currentMin = input[row][column];
                }    
        }
        return currentMin;
    }

    public static double getCurrentMax (double [][] input){    
        double currentMax = input[0][0];
        for (int row = 0; row < input.length; row++){
            for (int column = 0; column < input [row].length; column++){
                if (currentMax < input[row][column]){
                    currentMax = input[row][column];
                }
            }    
        }
        return currentMax;
    }
}

import java.io.*；
导入javax.swing.JOptionPane；
导入java.util.*；
导入java.util.StringTokenizer；
公共班机{
公共静态void main（字符串[]args）引发IOException{
String fname=“data.txt”；//读取数据文件以在数组中使用
String pass=JOptionPane.showInputDialog（“请输入”+
“要继续的密码：”；/*请用户输入要继续的密码
访问该文件*/
checkPass（pass）；//继续之前，请验证密码是否正确。
readData（fname）；//读取数据、打印输出并保存输出文件。
}
专用静态无效检查过程（字符串过程）
{
字符串密码=“INF260”；
int passCount=0；
if（pass.equals（password））{
System.out.println（“密码正确，继续…”）；
}
否则{
做{
pass=JOptionPane.showInputDialog（“请重新输入”+
“密码：”；
passCount++；
}而（！pass.equals（password）&&passCount<2）；
如果（！pass.equals（密码））{
System.out.println（“您已尝试输入”+
“密码次数太多。正在退出…”）；
系统出口（0）；
}
否则{
System.out.println（“密码正确，继续…”）；
}
}
}
公共静态void readData（字符串数据）引发IOException{
FileReader inputData=新的FileReader（数据）；
BufferedReader findNum=新的BufferedReader（inputData）；
字符串str=findNum.readLine（）；
整数计数=-1；
int countNum=0；
双倍合计=0；
双最小值=0；
双最大值=0；
双平均=0；
FileWriter writeFile=新的FileWriter（“sales.txt”）；
PrintWriter printFile=新的PrintWriter（writeFile）；
while（str！=null）
{
double num=double.parseDouble（str）；
如果（计数=0）{
countNum++；//要使用的接收计数器
}
str=findNum.readLine（）；
}
双精度[]输入=新双精度[countNum][10]；
总计=getCurrentTotal（输入）；/*这将获得总计
从方法getCurrentTotal*/
min=getCurrentMin（输入）；/*这将从
方法getCurrentMin*/
max=getCurrentMax（输入）；/*这将从
方法getCurrentMax*/
average=（total/countNum）；//计算平均值。
System.out.println（“今天的销售清单：”）；
for（int row=0；row输入[行][列]）
currentMin=输入[行][列]；
}    
}
返回电流最小值；
}
公共静态双getCurrentMax（双[]输入）{
双电流最大值=输入[0][0]；
for（int row=0；row// from your main method
String fname = "data.txt";
readData (fname);

// the method being called
public static void readData (String data[][]){           
   BufferedReader br = new BufferedReader(new FileReader(data));