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The last step is to bulletproof the application, we're going to make sure the application doesn't fail

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or crash no matter what happens right now, there are many places where unchecked exceptions could be

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thrown during the runtime and cross the application, but we can't allow that to happen.

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Let's run the app.

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And the first vulnerability is if the user enters the wrong and put the Atheros in input mismatch exception.

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And if we get an unchecked exception, it means we have to improve our code.

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And what we're missing is code that anticipates a scenario where the user may enter a value that is

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not an integer.

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So what I'll do is I'll apply conditional assignment here, I'll check if scanned on has next and if

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the next thing the user inputs is an integer, then we'll pick up the input using next and otherwise

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we'll assign it the value of 404.

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And how convenient is it that we already have a next line right here?

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Because if 404 returns, we still need to pick up the input.

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Otherwise things are going to get out of whack and next line can pick up anything.

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So that's perfect.

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Same thing here, if the next input that scanner reads is an integer.

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Then we'll pick it up, otherwise we'll just assign the value for for.

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And now before creating the object, I'll just say if either value is Foro for.

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Then just restart the wire loop.

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Rewriting the code.

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I'm going to say, don't know how beautiful.

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And the next vulnerability in the app is if the user index is outside the bounds of the array and the

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app throws an array index out of bounds, exception, unchecked exceptions are the result of badly written

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code.

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And what we're missing in the code is logic that anticipates the user indexing on a bounce.

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So what I'll do is I'll see if the aisle number is smaller than zero or bigger than six.

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Or if the column number is smaller than zero.

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Or bigger than two.

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Then the user is indexing outside the bounds of the array, so we have to restart the loop.

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If I index outside the bounds of the array, it just restarts the loop and doesn't crash, perfect.

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Last thing we might get is an illegal state exception if I try to remove from an empty cart, the app

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is going to throw an illegal state exception.

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This exception is thrown by the remove method, and that's because we shouldn't be calling the remove

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function when there's nothing in the cart that's just bad and I'm glad it crashed.

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It means we get to improve our code.

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So I'm going to add a method that returns a bullion named is empty.

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And it's going to return a boolean that indicates if the array list is empty.

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So back here, I'll say.

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If Kurt.

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Is empty.

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I'll restart the while loop.

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Try to remove from an empty cart.

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And we're all good.

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Now, what if I tried to check out an empty cart this time, the checkout method throws an illegal STD

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exception.

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That's because our app is calling checkout when there is nothing inside the cart.

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And that's just bad code.

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It's telling us to improve our code.

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So once again, will check.

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If Kurt.

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Is empty.

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Then restart the wire loop.

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And with this final line of code, I'm proud to say we're done building the shopping cart application,

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I'm going to run the app.

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And now I can just keep playing around with it with full confidence that it's always going to work.

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And it's going to keep letting me do my shopping, this app is really rewarding because it involves

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everything from two to you raise.

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We created objects of three different classes and we made them work together.

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We implemented exception handling, you learn how to write an equals method to compare it to objects,

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you've come this far and I hope you're proud of yourself.