Doesnt make sense

Question

I am very new to java. and i am taking it in university 1st year.. now.. we have labs to do but they dont tell us how to do em, they tell us to just do em... could someone please help me?
public class FoodItem {
private String description;
private double size;
private double price;
// Methods
// postcondition: creates a new object with data field
// values as specified by the arguments
public FoodItem(String desc, double aSize, double aP)
description = desc;
size = aSize;
price = aP;
// postcondition: sets description to the argument value
public void setDesc(String desc)
description = desc;
// postcondition: sets size to the argument value
public void setSize(double aSize)
size = aSize;
// postcondition: sets price to the argument value
public void setPrice(double aPrice)
price = aPrice;
// postcondition: returns the item description
public String getDesc() {
return description;
// postcondition: returns the item size
public double getSize() {
return size;
// postcondition: returns the item price
public double getPrice() {
return price;
// postcondition: returns a string representing the item state
public String toString() {
return description + ", size : " + size +
", price $" + price;
// postcondition: calculates and returns the unit pric
public double calcUnitPrice() {
return price / size;
now... that is what i have... but.... how do i do thesE?
a) Add a data field to store the total calories in a food item to the class
FootItem.
b) Add the methods setCal() and getCal().
c) Add a default constructor with no argument.
d) Add a constructor with two arguments: description and calories.
e) Add a constructor with 4 arguments: description, size, price, calories.
f) Modify the method toString() to return a string representing the state of an
object of class FootItem.
g) Modify class TestFoodItem to declare and create a new FootItem object
called dietCoke using the default constructor. Use the setter methods to
store the information that represents a 250 ml diet Coke that cost $1.25
with zero calories.
h) Modify class TestFoodItem again to add another object to represents a 250
ml regular Coke that cost $1.25 with 110 calories. Use the four parameters
constructor.
i) Display the attributes of these two objects.
If noone will help me with them... thats fine, it's totally up to you. I just do not understand any of this... i cannot find any of it in the notes.... and there is no text book..... any and all help is appreciated.

Answer 1

how do i add a default constructor with no argument?
public FoodItem() {
    // but what goes here?
}To figure out what the body of the constructor would be ask
yourself what would happen if you don't initialise description, size, price
as you did in the other constructor. (Give them initial values)
Is it a problem at all? (Test and see)
If it is what can you do about it?