Thread: Need Help Manipulating 2D Array

Hello. I need help with an assignment. The assignment requires me to take user input from a multi dimensional array. That input which is of each employees hours for monday - friday is output in a table.
It works with an array in which I have hard coded the values. I need to know how to make it so that the values can be from user input.
Thank you

import java.util.Scanner;
 
public class TimeBook  {
 
private int numberOfEmployees;
private int[][] hours; //hours[i][j] has the hours for
//employee j on day i.
private int[] weekHours; //weekHours[i] has the week's
//hours worked for employee i + 1.
private int[] dayHours; //dayHours[i] has the total hours
//worked by all employees on day i.
private static final int NUMBER_OF_WORKDAYS = 5;            // rows. 
private static final int MON = 0;
private static final int TUE = 1;
private static final int WED = 2;
private static final int THU = 3;
private static final int FRI = 4;
private static final int NUMBER_OF_EMPLOYEES = 3;           // textbook version has this in main as first line.
 
 
    public static void main(String[] args)
    {
        TimeBook book = new TimeBook(NUMBER_OF_EMPLOYEES);
        book.setHours();
        book.update();   
        book.showTable();
    }
    public TimeBook(int theNumberOfEmployees)
    {
    numberOfEmployees = theNumberOfEmployees;
    hours = new int[NUMBER_OF_WORKDAYS][numberOfEmployees];
    weekHours = new int[numberOfEmployees];
    dayHours = new int[NUMBER_OF_WORKDAYS];    
    }
    public void setHours()
    {
        hours[0][0] = 8; hours[0][1] = 0; hours[0][2] = 9;
        hours[1][0] = 8; hours[1][1] = 0; hours[1][2] = 9;
        hours[2][0] = 8; hours[2][1] = 8; hours[2][2] = 8;
        hours[3][0] = 8; hours[3][1] = 8; hours[3][2] = 4;
        hours[4][0] = 8; hours[4][1] = 8; hours[4][2] = 8;
    }
    public void update()
    {
        computeWeekHours();
        computeDayHours();
    }
    public void computeWeekHours()
    {
        for (int employeeNumber = 1; employeeNumber <=numberOfEmployees; employeeNumber++)
            {//Process one employee:
            int sum = 0;
            for (int day = MON; day <= FRI; day++){
                sum = sum + hours[day][employeeNumber - 1];
                //sum contains the sum of all the hours worked in
                //one
                //week by the employee with number employeeNumber.
                weekHours[employeeNumber - 1] = sum;
            }
            }
    }
    private void computeDayHours()
    {
        for (int day = MON; day <= FRI; day++)
        {//Process one day (for all employees):
            int sum = 0;
            for (int employeeNumber = 1;employeeNumber <= numberOfEmployees;
                   employeeNumber++)
            {
                sum = sum + hours[day][employeeNumber - 1];
                //sum contains the sum of all hours worked by all
                //employees on one day.
                dayHours[day] = sum;
            }
        }
    }
    public void showTable()
    {
        // HEADING BEGIN
        System.out.print("Employee \t");
        for (int employeeNumber = 1;employeeNumber <= numberOfEmployees;            // numberOfEmployees is 3. 
        employeeNumber++)
        {
            System.out.print(employeeNumber + "\t");
        }
        System.out.println("Total");                   //added to display totals after final employee number.
        System.out.println();                           //added to begin next line with day and hours beneath. 
        // HEADING END
 
        // ROWS BEGIN
        for (int day = MON; day <= FRI; day++)
        {
            System.out.print(getDayName(day) + " ");
            for (int column = 0; column < hours[day].length;
            column++)
            {
                System.out.print(hours[day][column] + "\t");
                //System.out.println(dayHours[day]);
            }
            System.out.println(dayHours[day]);          //added to display sum of all employee hours for the day under 'Totals' col.
            System.out.println( );
            //System.out.print("Total = ");             // displays total of each employee at bottom line for week. 
 
        }
        System.out.print("Total: \t\t");
        for (int column = 0; column < numberOfEmployees; column++)
        {
            System.out.print(weekHours[column] + "\t");
        }
        //Converts 0 to "Monday", 1 to "Tuesday", etc.
        // ROWS END
 
    }
    private String getDayName(int day)
    {
        String dayName = null;
        switch (day)
        {
        case MON:
        dayName = "Monday  \t";
        break;
        case TUE:
        dayName = "Tuesday \t";
        break;
        case WED:
        dayName = "Wednesday \t";
        break;
        case THU:
        dayName = "Thursday \t";
        break;
        case FRI:
        dayName = "Friday \t\t";
        break;
        default:
        System.out.println("Fatal Error.");
        System.exit(0);

How would you fill one variable with a value from the user?

How would you fill a single dimensional array with the word "FUN" for every element?

How would you fill a two dimensional array with the word "PARTY" for every element?

Break your overall problem down into smaller parts. Make a method that will get a valid user input, and assign it to a variable. Then make the code take that value and assign it to an element of an array. Then adapt that to fill the array. From there handle multiple dimensional arrays.

In the 'setHours()' method I have created this double for loop. It isn't working though because when I enter something like '8 7 9' for the employee's hours I get an error.

public void setHours()
    {
        Scanner keyboard = new Scanner(System.in);
        for(int dayhrs=0;dayhrs<=numberOfEmployees;dayhrs++)
        {
            for(int eachday=0;eachday<=NUMBER_OF_WORKDAYS;eachday++)
            {
                System.out.println("Enter day's hours followed by enter");
                hours[dayhrs][eachday] = keyboard.nextInt();
            }
        }
    }

I get an error.

If we don't know what error you are getting, there is little advice we can offer. Please post your current version of the code and error messages with your question so that everything is available to assist you.

Here is the current version of the code

import java.util.Scanner;
 
public class TimeBook  {
 
private int numberOfEmployees;
private int[][] hours; //hours[i][j] has the hours for
//employee j on day i.
private int[] weekHours; //weekHours[i] has the week's
//hours worked for employee i + 1.
private int[] dayHours; //dayHours[i] has the total hours
//worked by all employees on day i.
private static final int NUMBER_OF_WORKDAYS = 5;            // rows. 
private static final int MON = 0;
private static final int TUE = 1;
private static final int WED = 2;
private static final int THU = 3;
private static final int FRI = 4;
private static final int NUMBER_OF_EMPLOYEES = 3;           // textbook version has this in main as first line.
 
 
    public static void main(String[] args)
    {
        TimeBook book = new TimeBook(NUMBER_OF_EMPLOYEES);
        book.setHours();
        book.update();   
        book.showTable();
    }
    public TimeBook(int theNumberOfEmployees)
    {
    numberOfEmployees = theNumberOfEmployees;
    hours = new int[NUMBER_OF_WORKDAYS][numberOfEmployees];
    weekHours = new int[numberOfEmployees];
    dayHours = new int[NUMBER_OF_WORKDAYS];    
    }
    public void setHours()
    {
        Scanner keyboard = new Scanner(System.in);
        System.out.println("Enter work hours. ");
        for(int i=0;i<=NUMBER_OF_WORKDAYS;i++)
        {
            for(int j=0;j<numberOfEmployees;j++)
            {
                hours[i][j]=keyboard.nextInt();
            }
        }
 
    }
    public void update()
    {
        computeWeekHours();
        computeDayHours();
    }
    public void computeWeekHours()
    {
        for (int employeeNumber = 1; employeeNumber <=numberOfEmployees; employeeNumber++)
            {//Process one employee:
            int sum = 0;
            for (int day = MON; day <= FRI; day++){
                sum = sum + hours[day][employeeNumber - 1];
                //sum contains the sum of all the hours worked in
                //one
                //week by the employee with number employeeNumber.
                weekHours[employeeNumber - 1] = sum;
            }
            }
    }
    private void computeDayHours()
    {
        for (int day = MON; day <= FRI; day++)
        {//Process one day (for all employees):
            int sum = 0;
            for (int employeeNumber = 1;employeeNumber <= numberOfEmployees;
                   employeeNumber++)
            {
                sum = sum + hours[day][employeeNumber - 1];
                //sum contains the sum of all hours worked by all
                //employees on one day.
                dayHours[day] = sum;
            }
        }
    }
    public void showTable()
    {
        // HEADING BEGIN
        System.out.print("Employee \t");
        for (int employeeNumber = 1;employeeNumber <= numberOfEmployees;            // numberOfEmployees is 3. 
        employeeNumber++)
        {
            System.out.print(employeeNumber + "\t");
        }
        System.out.println("Total");                   //added to display totals after final employee number.
        System.out.println();                           //added to begin next line with day and hours beneath. 
        // HEADING END
 
        // ROWS BEGIN
        for (int day = MON; day <= FRI; day++)
        {
            System.out.print(getDayName(day) + " ");
            for (int column = 0; column < hours[day].length;
            column++)
            {
                System.out.print(hours[day][column] + "\t");
                //System.out.println(dayHours[day]);
            }
            System.out.println(dayHours[day]);          //added to display sum of all employee hours for the day under 'Totals' col.
            System.out.println( );
            //System.out.print("Total = ");             // displays total of each employee at bottom line for week. 
 
        }
        System.out.print("Total: \t\t");
        for (int column = 0; column < numberOfEmployees; column++)
        {
            System.out.print(weekHours[column] + "\t");
        }
        //Converts 0 to "Monday", 1 to "Tuesday", etc.
        // ROWS END
 
    }
    private String getDayName(int day)
    {
        String dayName = null;
        switch (day)
        {
        case MON:
        dayName = "Monday  \t";
        break;
        case TUE:
        dayName = "Tuesday \t";
        break;
        case WED:
        dayName = "Wednesday \t";
        break;
        case THU:
        dayName = "Thursday \t";
        break;
        case FRI:
        dayName = "Friday \t\t";
        break;
        default:
        System.out.println("Fatal Error.");
        System.exit(0);
        break;
        }
        return dayName;
    }
 
 
 
}

and the error I get when running it is this:
-------------------------------------------------
run:
Enter work hours.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 5
at employee.time.records.TimeBook.setHours(TimeBook.j ava:50)
at employee.time.records.TimeBook.main(TimeBook.java: 31)
Java Result: 1
BUILD SUCCESSFUL (total time: 15 seconds)

You understand an array of 5 elements would be numbered 0 1 2 3 4, right? The error says that you tried to access an element that does not exist. Either an index value of less than zero, or greater than size-1 (hint: the error message has this strange :5 on the end)

Figure out where the code is trying to access an element of the array that does not exist. If you can not see it in the code, add some printlns to see the values as the code runs. (or a debugger)

And now it works! Thank you very much for your help!
tumblr_lpqpkj3iAw1qlsz95o1_500.jpg

I am glad it works.

If this issue has been solved please mark the thread as solved. Ty