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The solution is going to cover part three, this test case tells us to check if an item is removed after

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being sold.

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So I'm going to write a unit test named Removed Item Test.

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And the item we're going to remove from the cart is.

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Krush.

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So ideally, calling remove should remove this object from the area list.

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And now we're going to make an assertion, assert false.

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And this test is going to pass if Calthorpe contains the crash, object returns false.

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And now inside Kageyama, we're going to write code to make the test fail.

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Public void remove.

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And the unit test implies we pass a string into our method and for now we'll do nothing.

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I want my test to fail.

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Good.

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Now we write code to make the test pass.

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The simplest code I can think of is to just create a loop that runs through the size of the array list.

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And if the item object at the index matches the name being Pastan.

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Will remove the item and index I.

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Let's run the test.

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And it passes.

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OK, here comes the more important question, can this be a refactored, can it be made simpler?

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And the answer to that is absolutely loop's are messy.

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Array lists have a remove if method.

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This items that remove if.

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The remove if method removes an item that matches the predicate that we write a predicate is just the

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function that returns true or false.

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So that means our lambda expression is going to receive an element as a parameter.

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Remember, it has an arrow key that points to code.

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And here we need to return a boolean and we're going to return a boolean that checks if the string of

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the element we're running through is equal to the name parameter.

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And the element that matches this predicate is going to be removed.

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And as you can see, using a functional approach is more elegant than using loops.

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So whenever it's possible, try to call a function that does the work for you.

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And as we refactor, we need to always run the unit test to make sure there aren't bugs.

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Hend Perfect's.

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Here, it removes the item and our assertion passes because the cart doesn't contain it anymore.

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Now, once again, can we refactor, that's a question you have to keep asking yourself until you're

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absolutely certain that your code is as simple as it's going to get in this case, if the code is only

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one line, then you can remove the curly brackets as well as the return keyword.

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Java's going to know you intend on returning a boolean because it's expecting a predicate.

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So that's pretty cool.

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I'll rerun the unit test.

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And Perfect's, the test passes, so I know that my code is working as intended now, once again, can

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we refactor?

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Nope.

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So far we're good and we can move on to the next test.