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Question

This是我的任務：

這裏是我的問題：

1. 我怎樣才能解決這個錯誤：

Exception in thread "main" java.lang.NumberFormatException: empty String at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1012) at java.lang.Double.parseDouble(Double.java:527) at extracredit.Main.readData(Main.java:72) at extracredit.Main.main(Main.java:27)

有沒有其他的問題，你可以看到這個程序？

這裏是我到目前爲止的代碼：

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; 
    } 
} 

Answer 1

// 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)); 

，我們這裏不兼容。

• FNAME是String
• 的方法，以一個String []作爲參數。
• 構造函數newFileReader（）接受一個字符串，而不是2d數組。

所有這三個應該是相同的數據類型。

How can I separate each "receipt" with zero (like shown in the image link above)?

您不必這樣做。您必須從該文件讀取其中的零。
我會建議你寫一個像這樣的方法：

public double [] readOneReceipt（BufferedReader reader）;

這個方法應該

• 讀一行行，直到遇到一個0項
• 它讀取轉換值，每次進入一個數（雙？）
• 將號碼存儲臨時結構體。
• 當您遇到「0」時，請創建一個正確大小的新數組，並將讀取的值複製到其中。

How can I write the output into a separate file?

隨着java.io.FileWriter

這IMO最難位的事實是，你被告知將數據存儲在一個二維數組，但你不知道什麼大小在讀取數據之前製作數組。 這意味着您要麼使用臨時動態結構，要麼讀取文件兩次 - 一次找出有多少個收據，以便您可以創建數組，然後再次實際讀取收據數據。

Answer 2

最好的解決辦法是：

• 研究你的課程材料
• 開始與像是剛剛讀取文件的問題的一個子集。
• 測試
• 遍歷：
  • 不斷改善和提高程序，直到它滿足所有要求。
  • 測試
• 一方面它在