Question

I am working on a program for class due today at midnight and I just can’t figure why it’s giving me this Null Point Exception error. I would really appreciate if you guys can look at my code and help me out.

The goal of the project is as follows..

• Program Statement: Write a Payroll class that uses the following arrays as fields:

  • employeeId – an array of 7 integers to hold employee id numbers. The array field should be initialized with the following numbers:
    1. 5658845
    2. 4520125
    3. 7895122
    4. 8777541
    5. 8451277
    6. 1302850
    7. 7580489
  • hours – An array of seven integers to hold the number of hours worked by each employee
  • payRate – An array of seven doubles to hold each employee’s hourly rate.
  • wages – An array of seven doubles to hold each employee’s gross wages.

  The class should relate the data in each array through the subscripts. For example, the number in element 0 of the hours array should be the number of hours worked by the employee whose ID number is stored in Element 0 of the employeeId array. That same employees pay rate should be stored in Element 0 of the payRate array. In addition to the appropriate accessor and mutator methods, the class should have a method that accepts an employee’s id number as an argument and returns the gross pay for that employee. Demonstrate the class in a complete program that displays each employee number and asks the user to enter the employee’s hours and pay rate. It should then display each employee’s id number and gross wages.

  • Input Validation : Do not accept negative values for numbers and numbers less than 6.00 for pay rate.

---

int[] employeeId;
int[] hours;
double[] payRate;
double[] wages;

Scanner kboard = new Scanner(System.in);

public ParrishPayroll(int[] ids){

    employeeId = new int[ids.length];
    // Copy the values in ids
    for (int index = 0; index < ids.length; index++)
        employeeId[index] = ids[index];

    System.out.println("Employee ID's");
    System.out.println(Arrays.toString(employeeId));

    System.out.println("Please enter the id number you would like to edit.");
        int input = kboard.nextInt();

        if(input == 5658845){
            int index = 0;
            setHours(index);
            }
        else if(input == 4520125){
            int index = 1;
            setHours(index);
            }
        else if(input == 7895122){
            int index = 2;
            setHours(index);
            }
        else if(input == 8777541){
            int index = 3;
            setHours(index);
            }
        else if(input == 8451277){
            int index = 4;
            setHours(index);
            }
        else if(input == 1302850){
            int index = 5;
            setHours(index);
            }
        else if(input == 7580489){
            int index = 6;
            setHours(index);
            }
        else {
            System.out.println("Invalid ID number!");

            }
}//end startSequence

public void setHours(int i){

    System.out.println("How many hours were worked?");
    hours[i] = kboard.nextInt();    
        if(hours[i] < 0){
            System.out.println("Please input a positive number.");
            kboard.nextInt(hours[i]);
            setPayRate(i);
        }
        else
            setPayRate(i);

}

public void setPayRate(int index){

    int input = index;

    System.out.println("What is the employee's pay rate?");
    payRate[input] = kboard.nextDouble();
        if(payRate[input] < 0){
            System.out.println("Please input a positive number.");
            payRate[input] = kboard.nextDouble();
            calcWages(input);
        }
        else if(payRate[index] < 6.00){
            System.out.println("Wages must be higher than $6.00.");
            payRate[input] = kboard.nextDouble();
            calcWages(input);
        }
}

public void calcWages(int index){

    int input = index;

    wages[input] = hours[input] * payRate[input];

}


public void getGross(int i){

    int input = i;

    if(input == 5658845){
        System.out.print("Employee number: " + input + " wages: " + wages[0]);
        }
    else if(input == 4520125){
        System.out.print("Employee number: " + input + " wages: " + wages[1]);
        }
    else if(input == 7895122){
        System.out.print("Employee number: " + input + " wages: " + wages[2]);
        }
    else if(input == 8777541){
        System.out.print("Employee number: " + input + " wages: " + wages[3]);
        }
    else if(input == 8451277){
        System.out.print("Employee number: " + input + " wages: " + wages[4]);
        }
    else if(input == 1302850){
        System.out.print("Employee number: " + input + " wages: " + wages[5]);
        }
    else if(input == 7580489){
        System.out.print("Employee number: " + input + " wages: " + wages[6]);
        }
    else {
        System.out.println("Invalid ID number!");
        getGross(input);
        }


   }


public static void main(String[] args){

    int[] idlist = {5658845, 4520125, 7895122, 8777541, 8451277, 1302850, 7580489};

    ParrishPayroll user1 = new ParrishPayroll(idlist);

    Scanner kboard = new Scanner(System.in);
    System.out.println("What employee would you like to see the gross wages for?");
    int i = kboard.nextInt();
    user1.getGross(i);    

}

Answer 1

It looks like you are not initializing the hours, payRate or wages variables, which means they are all null. When you call, say, hours[i] = kboard.nextInt() it will throw a NullPointerException because you can’t set the i th element of null.

Make sure you have a line like hours = new int[whatever] before you try to use the hours variable (same for the other two). You’ve got it right for employeeId, so follow that pattern.