java.lang.ArrayIndexOutOfBoundsException？

Question

I am currently teaching my self some basic Java through a text book and gave myself a "homework problem" but I'm having difficulty when writing to a .txt file of a method. It doesn't want to take more than 2 people. Here's a quick run down of what the method is meant to do:

1.) Collects the number of people the user would like to enter into the data file

2.) Collects the first and last name of each person in a two-dimensional array

3.) Collects a number of payments set by the user for each (separate) person that the user entered into an array.

4.) Then it calculates the average payment for each of the people entered into another array(so each person should have their own average)

5.) Lastly, it writes the data to a .txt file named "BusinessData.txt."

It seems to be working perfectly up until it tries to write more than 2 people into the .txt file. It's driving me nuts and I really would like to know how to fix this before moving on to the next couple of topics.

Here's the error message that I am getting when I try to add more than 2 people:

Exception in thread "main" java.lang.Array IndexOutofBoundsException: 3
at Business1.dataCollect(Business1.java:210)
at Business1.main(Business1.java:62)

I'd greatly appreciate any tips.

Here's the actual code:

import java.util.*;
import java.io.*;

public class Business1
{
    public static void main(String[] args) throws IOException
    {
        // Declare local variables
        int menuChoice;

        // Declare local objects
        Scanner input = new Scanner(System.in);

        // Display the program title
        System.out.println("\n\n\n\n\t\t\t\t***************************************\n"
                                +  "\t\t\t\t* Average Customer Payment Calculator *\n"
                                +  "\t\t\t\t***************************************\n\n\n");

        // Start of a do-while loop: Continues the program as long as the user doesn't choose to exit
        do
        {
            // Start of a do-while loop: Input Validation (menuChoice must be between 1 - 4)
            do
            {

                // Prompt user for menuChoice
                System.out.print("\tPlease enter an integer in accordance to the given choices:\n\n"
                                 + "\t(1) Collect and Erase Old Data\n"
                                 + "\t(2) Read Saved Data\n"
                                 + "\t(3) Append Old Data\n"
                                 + "\t(4) Exit Program\n\n"
                                 +"\tEnter Choice: ");

                menuChoice = input.nextInt();
                System.out.println("\n\n");


                // If menuChoice is equal to 1: Erase old Data and Collect and Write new data
                if(menuChoice == 1)
                {
                    try
                    {
                        dataCollect();
                    }

                    catch(IOException e)
                    {
                        System.out.println("Error");
                    }
                }
                // else if menuChoice is equal to 2: Read Saved Data
                else if(menuChoice == 2)
                {

                } 
                // else if menuChoice is equal to 3: Append Old Data
                else if(menuChoice == 3)
                {

                }
                // else if menuChoice is equal to 4: Exit Program
                else if(menuChoice == 4)
                {
                    System.out.println("\n\n\n\t\tGoodbye!\n\n\n");
                }

                // else display error message: Error. Please enter a number 1 - 4 
                else
                {
                    System.out.println("\n\nERROR. Please enter a number 1 - 4\n\n");
                }

            // End of do-while loop: Input Validation (menuChoice must be between 1 - 4)
            } while(menuChoice < 1 || menuChoice > 4);
        // End of a do-while loop: Continues the program as long as the user doesn't choose to exit
        } while(menuChoice != 4);
    }

    // Create a method named dataCollect
    public static void dataCollect() throws IOException
    {
        // Declare local variables
        int numPeople, numPayments /* array size for payments */;
        double totalPayments = 0, averagePayment;
        double [] paymentsArray  /* different payments */, averagePaymentsArray;
        String [][] namesArray /* First name, last name in array */;

        // Declare objects
        Scanner keyboard = new Scanner(System.in);


        // Prompt user for the number of people they would like to add to the records and store in variable numPeople
        System.out.print("\tHow many people would you like to add to your records?\n\n\tEnter an integer: ");
        numPeople = keyboard.nextInt();
        System.out.println("\n\n");

        // Initialize arrays
        namesArray = new String[numPeople][2];


        // Create a counter for the for-loop
        int count = 0;
        // For-loop will prompt user for first and last name of each person
        for(int i = 1; i <= numPeople; i++)
        {

            // Consume the remaining newline character
            keyboard.nextLine();

            // Prompt user for first name
            System.out.print("\tPlease enter the FIRST name of person #" + i  +": ");
            namesArray[count][0] = keyboard.nextLine();
            System.out.println("\n\n");

            //Prompt user for last name
            System.out.print("\tPlease enter the LAST name of person #" + i + ": ");
            namesArray[count][1] = keyboard.nextLine();
            System.out.println("\n\n\n");

            count++;
        }

        // Reset counter for the next for-loop
        count = 0;
        int count2 = 1; // Used to keep track of which payment number the user is inputing
        int count3 = 0; 
        int count4 = -1;


        // ****************************************************************
        // * Open file for input ******************************************
        // ****************************************************************

        PrintWriter outputFile = new PrintWriter("BusinessData.txt");
        outputFile.println("\t\t\tBusiness Data\n\n");
        outputFile.println("First Name\tLast Name\tP 1\t\tP 2\t\t P 3\t\tAverage Payments\n\n"
                        +  "------------------------------------------------------------------------------------------------------------------------------------------------------\n");

        // For-loop will ask for number of payments each person made while also collecting the value of each of those payments in a nested for-loop.
        for(int i = 0; i < numPeople; i++)
        {
            // Prompt user for first name
            System.out.print("\tPlease enter the number of payments made by " + namesArray[count][0] +" " + namesArray[count][1] + "(Put in 3 for now) : ");
            numPayments = keyboard.nextInt();


            System.out.println("\n\n");

            // Initialize array then reset it for the next person to come
            paymentsArray = new double[numPayments];

                for(int j = 0; j < numPayments; j++)
                {
                    // ****************************************************************
                    // * Open file for input ******************************************
                    // ****************************************************************

                    System.out.print("\n\n\tPlease enter payment value of payment #" + count2 + " that " + namesArray[count][0] +" " + namesArray[count][1] + " made: $");
                    paymentsArray[j] = keyboard.nextDouble();
                    System.out.println("\n\n");

                    // Increment counter
                    count2++;
                }

                    // ************************************************************************
                    // * Calculating Average Payment ******************************************
                    // ************************************************************************

                    // For loop for calculating average
                    for(int k = 0; k < numPayments; k++)
                    {
                        totalPayments += paymentsArray[k];
                    }

                    // Calculate the Average Payment
                    averagePayment = totalPayments/paymentsArray.length;

                    /**************************************************
                     ********** BUG LIES IN THE WRITING  **************
                    ***************************************************/


                    // nested for-loop will write data now otherwise it'll just be wiped out and overwritten by the next input
                    for(int l = 1; l < numPeople; l++)
                    {   

                        // Increment counter4
                        count4++;
                        // Output first name
                        outputFile.print(namesArray[count4][count3]);

                        // Increment counter3
                        count3++;

                        // Output last name
                        outputFile.print("\t\t" + namesArray[count4][count3] + "\t\t");
                        // Reset counter3
                        count3 = 0;


                        for (int m = 0; m < numPayments; m++)
                        {
                            outputFile.print(paymentsArray[m] + "\t\t");
                        }

                        outputFile.println(averagePayment + "\n\n");
                    }


             // Reset total Payments for the next iteration
            totalPayments = 0.0;

            // Increment the counter
            count++; 
        }
        outputFile.close();

    // End of dataCollect method
    }   

Answer 1

Running your code gives me Exception for 3+ users. ArrayIndexOutOfBoundsException thrown at

  outputFile.print(namesArray[count4][count3]);

Running in debug mode shows that namesArray[count4][count3] is pointing to a value which is not available .

count4 is incremented to out of bounds value because of the below loop.

I don't undertstand why you need this loop

for(int l = 1; l < numPeople; l++)
                { 
enter code here}

If you remove this it works fine.