How do I fix this java.lang.NullPointerException: null on my code?

Question

My teacher asked us to create a class named Pizza that stores information about a single pizza, which should contain:

Private instance variables that store the size of the pizza (small, medium, or large), the number of cheese, pepperoni and ham toppings.
Constructor(s) that set all of the instance variables.
Public methods to get and set the instance variables.
A public method name calcCost() that returns a double that is the cost of the pizza.

Pizza cost is determined by size. Small = $10 + $2 per topping. Medium = $12 + $2 per topping. Large = $14 + $2 per topping.

A public method named getDescription() that returns a String containing the pizza size, quantity of each cost and the pizza cost as calculated by calcCost().

Here is my class:

public class Pizza
{
     private String pizzaSize;
     private int numOfCheese;
     private int numOfPepperoni;
     private int numOfHam;

public Pizza (String a, int b, int c, int d)
{
    a = pizzaSize;
    b = numOfCheese;
    c = numOfPepperoni;
    d = numOfHam;
}

public String getSize()
{return pizzaSize;}

public int getCheese()
{return numOfCheese;}

public int getPepperoni()
{return numOfPepperoni;}

public int getHam()
{return numOfHam;}

public String getDescription()
{
    return ("Size: " + pizzaSize + "," + "\t" + "Cheese Toppings: " + numOfCheese + 
        "\t" + "Pepperoni Toppings: " + numOfPepperoni + "\t" + "Ham Toppings: " + 
        numOfHam + "\t");
}

public double calcCost()
{
    double cost = 0.0;
    int numOfToppings;
    int costOfToppings;
    if (pizzaSize.equals("Small"))
    {cost = 10.0;}
    else if (pizzaSize.equals("Medium"))
    {cost = 12.0;}
    else if (pizzaSize.equals("Large"))
    {cost = 14.0;}

    numOfToppings = ( (numOfCheese + numOfPepperoni) + numOfHam);
    costOfToppings = (numOfToppings * 2);
    cost += numOfToppings;
    return cost;
    }
}

Here is the demo driver that goes with it:

    public class Question11
{
    public static void main(String[] args)
    {
        // Create a few sample pizzas and output their prices
        Pizza supreme = new Pizza ("Large",1,2,1);
        Pizza cheese = new Pizza ("Medium",2,0,0);
        Pizza pepperoni = new Pizza ("Small",0,0,2);
        System.out.printf( "%-75sCost: $%5.2f %n",     supreme.getDescription(), supreme.calcCost() );
        System.out.printf( "%-75sCost: $%5.2f %n", cheese.getDescription(), cheese.calcCost() );
        System.out.printf( "%-75sCost: $%5.2f %n", pepperoni.getDescription(), pepperoni.calcCost() );
    }
 } // Question 11

The java.lang.NullPointerException: null error comes up on the size.equals part and the supreme.calcCost() for the driver. Any help is appreciated, and yes I read the other java.lang.NullPointerException forums/questions on this site and I am still confused.

@Simze Not possible, probable. But let's try to fix it anyway :-) — Tim Biegeleisen, Dec 04 '15 at 06:09

score 2 · Answer 1 · edited Dec 04 '15 at 06:11

2

public Pizza (String a, int b, int c, int d) {
    pizzaSize = a;       // assigns a value to pizzaSize
    numOfCheese = b;
    numOfPepperoni = c;
    numOfHam = d;
}

Change your Pizza constructor.

edited Dec 04 '15 at 06:11

Tim Biegeleisen

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answered Dec 04 '15 at 06:10

SatyaTNV

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Did I really mess up on the easiest part?!? – Michael Lehman 11th Grade Dec 04 '15 at 06:11

score 1 · Answer 2 · answered Dec 04 '15 at 06:11

1

your constructor goes backwards, you're assigning the variables from the method instead of the class fields:

public Pizza (String a, int b, int c, int d)
{
    a = pizzaSize;
    b = numOfCheese;
    c = numOfPepperoni;
    d = numOfHam;
}

should be:

public Pizza (String a, int b, int c, int d)
{
    pizzaSize = a;
    numOfCheese = b;
    numOfPepperoni = c;
    numOfHam = d;
}

I also suggest giving it more meaningful names than a, b, c, d

answered Dec 04 '15 at 06:11

Nir Levy

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Thank you. I can't believe it was something so simple. Haha I was trying for like 2 hours and it was just that. Ughh. – Michael Lehman 11th Grade Dec 04 '15 at 06:13

How do I fix this java.lang.NullPointerException: null on my code?

2 Answers2