Question

This is my assignment:

Here are my questions:

1. How can I fix this error:

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)

2. Are there any other problems that you can see with this program?

Here’s my code so far:

    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)); 

We have an incompatibility here.

• fname is a String
• The method takes a String[] as a parameter.
• the constructor newFileReader() takes a string, not 2d array.

All of these three should be the same data type.

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

You don’t have to. You have to READ from that file with the zeros in it.
I would recommend you write a method something like this:

public double[] readOneReceipt(BufferedReader reader);

This method should

• Read line by line until it encounters a 0 entry
• for each entry it reads convert the value into a number (double?)
• Store the number in a temporary structure.
• When you encounter the ‘0’, create a new array of the correct size and copy the read values into it.

How can I write the output into a separate file?

With a java.io.FileWriter

The hardest bit of this IMO is the fact that you are told to store the data in a 2d array, but you don’t exactly what size to make the array until you’ve read the data. Which means that you either use a temporary dynamic structure, or read the file twice – once to find out how many receipts there are so that you can make the array, and then again to actually read the receipt data.