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We need to fix our constructor so that it can update every single field, the car class, it's five

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fields.

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So when you create an object of the car class, the object is going to define Fifield's.

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However, your constructor only updates four of them.

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In this lesson, you're going to fix your constructor.

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Your constructor is missing a parameter, it's the constructor's job to update every field in the object,

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so your constructor needs to receive another parameter string parts.

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And now set the array field from the current object.

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This parts is equal to a copy of the perimeter erased that copy of.

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We're going to get a copy of the Pozza ray.

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And how much of it do we want to copy all of it parts just like remember to avoid setting array variables

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equal to each other, otherwise you'll fall into a reference trap.

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We talked about this table in Module one, but it's also in your cheat sheet.

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So inside main create a new array of parts, string parts.

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And it's going to store two parts, Tirhas and Keese.

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And the reason we have errors is because of the constructor is now expecting five parameters.

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And we're only passing in four values.

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So make sure to pass in the part array into each constructor call.

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OK, we're good.

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And before we run the code removed, the individual calls to drive the drive action is going to play

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its role later.

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Right now, we don't need it.

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Can't run the code.

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And these are not spare parts, is it?

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Not anymore, but instead of printing a reference to the array we're going to use to string to print

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the contents of the array arrays.

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To string.

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Nissan parts.

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Perfect.

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We're making a lot of progress.

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You said Nissan equal to when you object and passed in five values, Java runs the constructor with

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five parameters.

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The parts parameter copies, the value inside the parts argument, the reference.

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So the parts parameter and parts arguments share a reference to the same array.

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Every field updates with a new value.

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But notably, we set the parts field equal to a copy of the array.

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Now, I need to tell you to pay attention to the reference trap, the reference trap occurs when you

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mishandle arrays or objects.

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What would happen if we directly set the parts field equal to the parts?

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Brammer.

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Let's try this out in our code test that parts equal parts.

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This is dangerous.

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Now, the argument.

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The perimeter and field alshehri reference to the same array.

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By mistake, let's assume I changed index one from the outside variable parts.

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I'll change the next one and set it equal to a written.

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Do you see what I mean?

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I meant only update the outside variable, the argument we Pastan, but the Nissan field changed as

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well.

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Have a look, you said Nissan equal to a new object and passed in five values, Gever runs the constructor

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with five parameters.

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The parts parameter copies, the value inside the parts argument, a reference.

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So the parts parameter and parts arguments, a reference to the same array, we said every field equal

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to a parameter.

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The party field copies the value inside the parts parameter, also a reference.

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Now the argument parameter and field share a reference to the same array.

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The parameter only exists inside the constructor.

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So eventually it falls out of scope.

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But the field and outside variables still point to the same array.

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And that's why modifying the outside variable directly affected the state of my field.

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With that being said, I need to warn you that the reference drop is a recipe for bugs, when many variables

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reference the same thing, your application's behavior becomes unpredictable.

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Your variables are going to start changing when you don't expect them to.

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And you're always going to scratch your head saying what's going on?

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To avoid this headache, it's really simple, it should be really careful about how you handle arrays

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and objects.

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I encourage you to follow my tables and pay attention to the reference Trappe.

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So once again, I'm going to set the field equal to a copy of the parameter.

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This time around, changing the outside variable should have no effect on the field, a straight out.

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And there you go.

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All right, we have to make the field private again, every field needs to be private.

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The array field is no exception.

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And now we have areas in Maine you cannot access a private field, and that's good, you should never

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have direct access to a field.

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So for now, all we can do is delete the print statements and we're going to add get her in the next

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lesson.

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In this lesson, you fixed your constructor, the constructor is missing a parameter, so you added

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a parts parameter.

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Now your constructor is all good because as soon as you create a new object, your constructor updates

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every field inside of it.