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The goal of this workbook was to quality control the item in machine classes, because if you're on

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the out the way it is.

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Some of the items have negative prices, negative quantities and blank names.

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Once again, these values don't make any sense and the caller should be forbidden from passing them.

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So when the item constructor, we're going to start by throwing an illegal argument exception, if the

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name is blank, so if name is equal to null.

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Or if the name is blank.

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Throw new.

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A legal argument, exception name cannot be null or blank.

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We're going to throw another exception if the price is less than zero, so if the price is less than

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zero, there are a new illegal argument exception.

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Price cannot be less than zero.

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We need to throw another exception if the quantity is less than zero.

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In which case will once again throw a new illegal argument, exception quantity cannot be less than

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zero.

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Katri around the code.

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The constructor forbids the caller from passing a legal values.

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That's good.

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This unchecked exception is forcing us to fix our code.

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So we're going to copy over the values from the workbook.

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Rerunning, running the app.

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And now we're good.

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Remember that centers are another place where the color may pass on illegal values, so we need to apply

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quality control there as well.

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So inside set name right through another illegal argument, exception, if the caller passes a name

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that is no or a blank.

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There are new legal argument, exception name cannot be null or blank.

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We'll do the same thing and set price if the culture passes a price that is less than zero, we'll throw

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a new illegal.

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Are you an exception?

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Price cannot be less than zero.

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Last one quantity, if they pass a quantity that is less than zero, throw a new illegal argument,

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exception quantity cannot be less than zero.

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Kate, now in the machine class, there is no need to throw a legal argument, exceptions in the constructor

35
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again, worst thing that could happen is a null being passed, but the output already throw a null pointer

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exception and the same can be said for set item.

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But what if the caller passes an invalid index here?

38
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Well, once again, the code would already throw an array index out of bounds exception.

39
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Same thing can be said about the center.

40
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So throwing another exception wouldn't make any sense.

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However, we can expect an illegal argument right here.

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There's a chance the caller may pass on an item with a quantity of zero.

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And in such a case, we need to index the item that they're interested in.

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And check if it's quantity is equal to zero.

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If that's the case, we need to throw an illegal argument exception.

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But says cannot dispense an item with a quantity of zero.

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That's all for a legal argument, exceptions.

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What about illegal state exceptions?

49
00:05:01,190 --> 00:05:05,990
Well, looking at this class, I can't really think of a scenario when a machine object can call a method

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at a bad time.

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Basically, the machine object would always be in a valid state to call any of its methods, and that's

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really it.

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You had to check points to the item in machine and classes, and every checkpoint forbids the caller

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from misusing the methods or constructor's.