## Explaining the Sort thing in the Cart


This code is sorting a list of shopping cart items by price using Java's Collections.sort method. Let me break it down:

```java
Collections.sort(cart, new Comparator<CartItem>() {
    @Override
    public int compare(CartItem item1, CartItem item2) {
        return Double.compare(item1.getPrice(), item2.getPrice());
    }
});
```

Here's what each part does:

1. `Collections.sort(cart, ...)` - This is calling Java's built-in sort method on a collection named "cart" which contains CartItem objects.

2. `new Comparator<CartItem>() { ... }` - This creates an anonymous inner class that implements the Comparator interface specifically for CartItem objects. The Comparator defines how two CartItems should be compared.

3. `@Override public int compare(CartItem item1, CartItem item2)` - This overrides the compare method from the Comparator interface. It takes two CartItem objects and returns an integer that indicates their relative ordering.

4. `return Double.compare(item1.getPrice(), item2.getPrice());` - This compares the prices of the two cart items using Double.compare (which handles special cases like NaN values properly). It will return:
   - A negative value if item1's price is less than item2's price
   - Zero if the prices are equal
   - A positive value if item1's price is greater than item2's price

After this code executes, the "cart" collection will be sorted in ascending order by price, with the cheapest items first and the most expensive items last.