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The goal of this workbook is the quality control, the car and dealership classes.

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Because if you're on the out the way it is.

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Both cars have negative price values and blank values, and these values don't make any sense and the

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color should be forbidden from passing them.

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So in the car constructor going to throw an illegal argument exception if the price is less than zero.

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Throw a new illegal argument, exception.

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Price cannot be less than zero.

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We're going to throw another exception if the make is no blank, if you make is equal to no or if the

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make is blank.

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Throw new.

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A legal argument, exception.

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Make cannot be null or blank.

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And if you rerun the code.

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The first checkpoint crashes the app, the price cannot be less than zero, so we need to pass a valid

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price values into the constructor.

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And the second checkpoint crashes, the app make cannot be null or blank.

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Pass valid, make values into the constructor, I'm going to put Nissan and Toyota.

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And by this point, the caller has been forced to pass incorrect values into the constructor.

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And so if you rerun the code, the second car's value still doesn't make any sense.

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The center is another place where quality control needs to take place.

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So inside set make I'm going to throw another illegal argument, exception, if the caller passes and

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make that is blank or null.

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There are new.

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A legal argument, exception.

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Make cannot be null or blank.

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Rerun the code and now the checkpoint and set may crash the app, it forces the color you to pass a

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valid make value to the set, make setar the stooges that.

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OK, good, but clearly the price setter is another place that needs quality control.

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So inside set price, I'm going to say if price is less than zero.

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Then I'll throw a new illegal argument exception.

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Price cannot be less than zero.

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Rerun the code.

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And now the checkpoint and set price crashes.

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The app, it forces the caller to pass a valid price value to the set price setter.

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I run the code again.

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And beautiful.

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Now we need to investigate the dealership class, so inside the class, there is no need to throw a

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legal argument, exceptions anywhere.

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Worst thing that could happen is someone could pass on a knowledge of the instructor, but the app would

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already throw a null pointer exception.

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The same can be said for said car.

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But what if the caller passes an invalid index here?

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Well, the code would already throw an array index out of bounds exception, so you throwing another

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unchecked exception wouldn't make any sense.

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What about an illegal state exception?

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Well, let me ask you this, does that make sense for a dealership to call the sale method if there

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are no cars inside?

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Absolutely not.

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So if the dealership is empty, then it's not in a valid state to call the sale method.

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So what I'm going to do is create a separate method called exempting.

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And it's going to loop through the array.

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And if any of the objects is not known.

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Then you're going to return false and break the loop.

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Otherwise, if they all end up being null, then the dealership is empty and will return true.

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And now back here, I can say if this if the current object that's calling this method is empty.

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Then throw an illegal state exception.

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Canacol sell when dealership is empty.

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And that's all you had to checkpoints to the car dealership classes, and now each checkpoint forces

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the caller to invoke the methods and constructors properly.