(a) The UML Diagram for the GroceryItem class.

+--------------------------------------------------------+
|      GroceryItem                                       |
+--------------------------------------------------------+
| - code : int                                           |
| - name : String                                        |
| - price : double                                       |
| - quantity : int                                       |
+--------------------------------------------------------+
| + GroceryItem(c : int, n : String, p : double, q : int)|
| + getCode() : int                                      |
| + getName() : int                                      |
| + getPrice() : int                                     |
| + setPrice(p : int)                                    |
| + toString() : String                                  |
+--------------------------------------------------------+


(b) The GroceryItem class.
    
public class GroceryItem
{
    public int code;
    public String name;
    public double price;
    public int quantity;
   
    public GroceryItem(int c, String n, double p, int q) 
    {
        code = c;
        name = n;
        price = p;
        quantity = q;
    }

    public double getPrice()
    {
        return price;
    }

    public void setPrice(double p)
    {
        if (p > 0.00)
            price = p;
    }

    public String toString()
    {
        return code + " " + name + " " + price + " " + quantity;
    }
}

//(c) The main class to test the GroceryItem class.
    
public class Main
{
    public static void main(String[] args)
    {
        GroceryItem x = new GroceryItem(3542534, "Milk", 2.79, 2);
        System.out.println(x);
        System.out.println(x.getPrice());
        x.setPrice(2.99);
        System.out.println(x);
    }
}

//(d) Here is the output:
3542534 Milk 2.79 2
2.79
3542534 Milk 2.99 2