NullPointerException when passing an array

[Rick]

I get a NullPointerException error when trying to run my program. I
think I am doing something wrong when copying the array, but am not
seeing what. Here is what I have and I marked where the error is
occuring.

/* The Client class ...
*/

public class Client
{

public static void main(String args[])
{

double order1Total, order2Total = 0.0;

// Create objects

// Products
Product p1 = new Product(1, "Computer", 350.00);
Product p2 = new Product(2, "Printer", 40.00);
Product p3 = new Product(3, "Scanner", 45.50);
Product p4 = new Product(4, "Digital Camera", 150.99);

// Line Items
// structure (item number, quantity, product)
LineItem li1 = new LineItem(1, 1, p1);
LineItem li2 = new LineItem(2, 2, p3);
LineItem li3 = new LineItem(3, 1, p1);
LineItem li4 = new LineItem(4, 3, p3);
LineItem li5 = new LineItem(5, 2, p4);

// Orders
LineItem[] order1Items = {li1, li2};
LineItem[] order2Items = {li3, li4, li5};
java.util.Date date1 = new java.util.Date();
java.util.Date date2 = new java.util.Date();
Order o1 = new Order(1, date1, order1Items); // THIS LINE IS GIVING
ME AN ERROR
Order o2 = new Order(2, date2, order2Items);

order1Total = o1.computeOrderTotal();
System.out.println(order1Total);
}

}





/* The Order class ...
*/

public class Order
{
private int orderNumber;
private java.util.Date orderDate = new java.util.Date();
private LineItem[] orderItems;


// Default contructor
Order()
{
}

// Constructor with parameters
Order(int newOrderNumber, java.util.Date newOrderDate, LineItem[]
newOrderItems)
{
orderNumber = newOrderNumber;
orderDate = newOrderDate;
for (int i = 0; i < newOrderItems.length; i++)
{
orderItems = newOrderItems; // THIS LINE IS GIVING ME AN ERROR
}
}

public double computeOrderTotal()
{
double orderTotal = 0.0;
for (int i = 0; i < orderItems.length; i++)
{
orderTotal += orderItems.computeLineItemTotal();
}

return orderTotal;
}

}






/* The LineItem class ...
*/

public class LineItem
{
private int itemNumber;
private int quantity;
private Product lineProduct;

// Default contructor
LineItem()
{
}

// Constructor with parameters
LineItem(int newItemNumber, int newQuantity, Product newLineProduct)
{
itemNumber = newItemNumber;
quantity = newQuantity;
lineProduct = newLineProduct;
}

public double computeLineItemTotal()
{
double lineTotal = 0.0;
lineTotal = quantity * lineProduct.getProductPrice();
return lineTotal;
}

}

 

[Jean-Francois Briere]

In the Order constructor you forgot to instantiate the orderItems field
before using it:

Order(...)
{
...
// instantiate orderItems
orderItems = new LineItem[newOrderItems.length];
for (...)
...
}

Regards

 

[Michael Rauscher]

I get a NullPointerException error when trying to run my program. I
think I am doing something wrong when copying the array, but am not
seeing what. Here is what I have and I marked where the error is
occuring.

The problem is that orderItems == null (in class Order). Allocate some
memory for it, e. g.

orderItems = new LineItems[newOrderItems.length];

Bye
Michael