Thread: Default Write a Java program to simulate an online shopping cart.

Look at the code for the CartItem class and find its constructors. Then write the new statement to use one of them.

I have tried using them but it is not working.

Please copy and post the code where you tried and the error messages you get.

Copy the constructor definition
and the new statement you are trying to use and paste them one above the other. That will allow you to compare the required arguments with the ones you are using and see what is wrong. For example:

  public SomeClass(int anInt) { //  constructor definition statement
 
  = new SomeClass("aString");  // invalid call - arg should be int not String
 
  = new SomeClass(123); // valid  - arg is int

all three lines of that code should go in

No. Those lines of code where an example, not part of your code.

Copy all the constructor definition statements
and the new statement you are trying to use
and paste them here in the thread, one above the other.

Please copy and paste the lines here, no images.

Change case 2 so its new statement uses the same type of arguments as for the new statement in case 1.

Exception in thread "main" java.lang.NullPointerException
at java.lang.String.<init>(Unknown Source)
at CartItem.<init>(CartItem.java:16)

There is a variable with a null value on line 16. Look at line 16 in the your source and see what variable is null. Then backtrack in the code to see why that variable does not have a valid value.
If you can not tell which variable it is, add a println just before line 16 and print out the values of all the variables on that line.