Help with Error Exception in thread "main" java.lang.NullPointerException

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 import java.text.DecimalFormat;

import javax.swing.JOptionPane;
 
public class PayrollSystemTest {
 
   public static void main( String[] args )

   {

      String workerType;

      String first;

      String last;

      String ssn;

      int month;

      int day;

      int year;

      float salary;

      float rate;

      float hourlyWage;

      float hours;  
 
      float sales;
 
      DecimalFormat twoDigits = new DecimalFormat( "0.00" );
 
      // create Employee array

      Employee employees[] = new Employee[ 5 ];
 
      // generically process each element in array employees

      for ( int empNo = 1; empNo <=5; empNo++ ) {
 
    workerType=JOptionPane.showInputDialog(

       "Please enter the type of worker:\n\n" +

       "Salaried\nHourly\nCommission\n" +

       "Base Plus Commission");
 
       if(workerType.equalsIgnoreCase("Salaried")){

           first=JOptionPane.showInputDialog("Enter employee " + empNo + 

              " first name: ");

        last=JOptionPane.showInputDialog("Enter employee " + empNo +

              " last name: ");

        ssn=JOptionPane.showInputDialog(

            "Enter employee " + empNo + " ssn: ");

        month=Integer.parseInt(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " birth month(1-12): "));

        day=Integer.parseInt(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " birth day(1-31): "));

        year=Integer.parseInt(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " birth year(yyyy): "));

        salary=Float.parseFloat(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " weekly salary: "));

        employees[empNo-1] = new SalariedEmployee(first, last,

              ssn, month, day, year, salary);

       }
 
       else if(workerType.equalsIgnoreCase("Hourly")){

        first=JOptionPane.showInputDialog("Enter employee " + empNo + 

              " first name: ");

        last=JOptionPane.showInputDialog("Enter employee " + empNo +

              " last name: ");

        ssn=JOptionPane.showInputDialog(

            "Enter employee " + empNo + " ssn: ");

        month=Integer.parseInt(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " birth month(1-12): "));

        day=Integer.parseInt(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " birth day(1-31): "));

        year=Integer.parseInt(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " birth year(yyyy): "));

        hourlyWage=Float.parseFloat(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " hourly wage: "));

        hours=Float.parseFloat(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " hours worked: "));

        employees[empNo-1] = new HourlyEmployee(first, last, ssn,

            month, day, year, hourlyWage, hours);

       }
 
       else if(workerType.equalsIgnoreCase("Commission")){

        first=JOptionPane.showInputDialog("Enter employee " + empNo + 

              " first name: ");

        last=JOptionPane.showInputDialog("Enter employee " + empNo +

              " last name: ");

        ssn=JOptionPane.showInputDialog(

            "Enter employee " + empNo + " ssn: ");

        month=Integer.parseInt(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " birth month(1-12): "));

        day=Integer.parseInt(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " birth day(1-31): "));

        year=Integer.parseInt(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " birth year(yyyy): "));

        sales=Float.parseFloat(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " weekly sales: "));

        rate=Float.parseFloat(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " commission rate: "));

        employees[empNo-1] = new CommissionEmployee(first, last,

            ssn, month, day, year, sales, rate);

       }
 
       else if(workerType.equalsIgnoreCase("Base Plus Commission")){ 

        first=JOptionPane.showInputDialog("Enter employee " + empNo + 

              " first name: ");

        last=JOptionPane.showInputDialog("Enter employee " + empNo +

              " last name: ");

        ssn=JOptionPane.showInputDialog(

            "Enter employee " + empNo + " ssn: ");

        month=Integer.parseInt(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " birth month(1-12): "));

        day=Integer.parseInt(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " birth day(1-31): "));

        year=Integer.parseInt(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " birth year(yyyy): "));

        sales=Float.parseFloat(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " weekly sales: "));

        rate=Float.parseFloat(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " commission rate: "));

        salary=Float.parseFloat(JOptionPane.showInputDialog(

            "Enter employee " + empNo + " base salary: "));

        employees[2] = 

               new BasePlusCommissionEmployee(first, last, ssn, month,

            day, year, sales, rate, salary);

       }
 
     }
 
    // initialize array with Employees

      //employees[ 0 ] = new SalariedEmployee( "John", "Smith",

      //   "111-11-1111", 1000, 1, 1, 1960 );

      //employees[ 1 ] = new CommissionEmployee( "Sue", "Jones",

      //   "222-22-2222", 12000, .05, 2, 1, 1962 );

      //employees[ 2 ] = new BasePlusCommissionEmployee( "Bob", "Lewis",

      //   "333-33-3333", 10000, .03, 500, 3, 1, 1963 );

      //employees[ 3 ] = new HourlyEmployee( "Karen", "Price",

      //   "444-44-4444", 20., 40, 4, 1, 1964 );

      //employees[ 4 ] = new SalariedEmployee( "Bruce", "Chiesa",

      //   "555-55-5555", 1000, 11, 1, 1961 );
 
        String output ="";
 
        for(int i=1; i<employees.length+1; i++){

           output += employees[i-1].toString();
 
         // determine whether element is a BasePlusCommissionEmployee

         if ( employees[ i-1 ] instanceof BasePlusCommissionEmployee ) {
 
            // downcast Employee reference to

            // BasePlusCommissionEmployee reference

            BasePlusCommissionEmployee currentEmployee =

               ( BasePlusCommissionEmployee ) employees[ i-1 ];
 
            double oldBaseSalary = currentEmployee.getBaseSalary();

            output += "\nold base salary: $" + oldBaseSalary;
 
            currentEmployee.setBaseSalary( 1.10 * oldBaseSalary );

            output += "\nnew base salary with 10% increase is: $" +

               currentEmployee.getBaseSalary();
 
         } // end if
 
         output += "\nearned $" + employees[ i-1 ].earnings()*4 + "\n";
 
      } // end for
 
      // get type name of each object in employees array

      for ( int j = 1; j < employees.length+1; j++ )

         output += "\nEmployee " + j + " is a " +

            employees[ j-1 ].getClass().getName();
 
      JOptionPane.showMessageDialog( null, output );  // display output

      System.exit( 0 );
 
   } // end main
 
} // end class PayrollSystemTest

error is on this line on 148

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output += employees[i-1].toString();

May 4 '08 #1

Subscribe Post Reply

2462

Laharl

849

Expert 512MB

i goes from 1 to employees.length+1, so i-1 goes from 0->employees.length. However, because arrays are zero-indexed, employees[employees.length] is the employees.length+1'th item. Thus, you're outside your array. Quite frankly, I'm surprised you got a NullPointerException, as you should probably have gotten an ArrayIndexOutOfBoundsException first when it tries to resolve the element.

May 4 '08 #2

gator6688

How do I fix it? Do I make i=0?

May 4 '08 #3

JosAH

11,448

Expert 8TB

How do I fix it? Do I make i=0?

See if there are actual employees in your array:

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for (int i= 0; i < employees.length; i++)

   System.out.println(i+": "+employees[i]);

If there is an employee present at slot i something will be printed, otherwise just
'null' will be printed. You attempt to override the toString() methond so something
sensible should be printed if an employee is printed.

Als note how the little loop above iterates over the array, i.e. there is no need to
start from 1 and subtract one from the index value again in the body of the loop.

kind regards,

Jos

May 4 '08 #4

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