Question

I am trying to create a program for an online Java course. This program includes an Employee class and a Name class. I have to create multiple Employee objects and prompt the user to enter the employee’s name. I am storing all the Employee objects in an employee array.

Here’s the code:

    //Creates employee array with the number of array elements being however many          
    //employees there are:
    Employee employee[] = new Employee [ numEmp ];

    for( int j = 0; j < numEmp; j++ )
    {
        System.out.println( "Please enter the first name of employee number "
                + ( j + 1 ) );
        Scanner input2 = new Scanner( System.in );
        String nameF = input2.nextLine();

        //This should set the employee object at employee array element "j" to the          
        //String nameF
        employee[ j ].setFirstName( nameF );

The problem is that the compiler, while running the program, says that the last line is a NullPointerException.
I’m not sure what I am doing wrong. Any suggestions?

Thanks!
-Sean

Answer 1

You created a new array with a size of numEmp, but the default value for each element is null. This means that the array initially contains numEmp null references. You need to use new to instantiate each Employee object before you can call methods on them.

You can either do this immediately after you create the array:

Employee employee[] = new Employee [ numEmp ];
for( int j = 0; j < numEmp; j++ )
{
    employee[j] = new Employee();
}

Or you could do it inside your existing loop, just before you first need to use the object:

employee[j] = new Employee();
employee[j].setFirstName(nameF);