All language subtitles for 027 Step 3 - Getter_en

If a class has failed, you need to add getas.

The cars is private, as it should be.

This means we can't access the field from outside.

So in this lesson, we're going to to get her.

The dealership class has one field, so we need to add one Geter.

So should ever get her be called get cars.

I hope you guessed the answer no, because let's imagine a scenario where I only want to access the

car at index zero, get cars, would create copies of every object in the car's array, but I only need

one of them.

This is a waste of memory.

When you create new copies of objects, it's not free.

It takes up memory.

It takes up space in your computer.

And so what if my array has a thousand cars?

Are you going to copy a thousand car objects, return them for the sake of accessing one?

Once again, this is typical to a class that manages an array of objects.

You just never know how many objects are going to be inside of that array.

And so it doesn't make sense to return every object at once.

Instead, the gutter is going to return one car object from an index of your choice.

So inside your dealership class at the get or get car public, it's going to return a car object.

Its name will be Get Car and it will take one parameter, the index of the car you want to get.

Finally, return the car object found at the index chosen by the user.

And now we can access the cars that we want.

In Maine and get the car object at index zero.

And the GETER is going to return the card index zero.

Pretty simple.

Let's print the new car object and make sure everything works fine.

And nice, when you print an object, Java knows to check if there's a two string method that returns

a string of every field.

Sounds great, right?

Let's update the new cars, clarefield new car at color.

Blue.

And then we're going to access another copy of the car object that in zero and print that object instead.

Well, what happened, this is bad, I change the outside variable, but the object at Index zero,

the cars feel changed as well.

If you return the object, Jaba returns a copy of what's inside the element and what's inside is a reference.

The letter is supposed to protect your field, but it returns a reference that points directly to one

of the objects.

This defeats the purpose of a letter.

Now the outside variable and field share a reference to the same object.

This is the last reference trap, reference trap for your Geter should not return an object directly.

The pitfall is that the outside variable and field are going to share a reference to the same object.

The solution is simple return a new copy of the object.

This table is in your cheat sheet, so we're going to return a new car object.

And in brackets, put the source object you want to copy values from we would like to copy values from

the car object and the index chosen by the user and right after creating a new car object or passing

any source object so Java knows to run the copy constructor, that receives one as a parameter.

And it's going to copy every field value from the source object into the one we just created.

And then the GETER is going to return a new copy, which gives me comfort, because now I know that

there's no way any of the objects inside the cars field are going to leak across the gutter, keeps

our field safe by returning copies of the underlying car objects.

Anyways, run the code.

And sweet, changing the outside variable has no effect on the field.

That's because the getter returns a copy of the object we're trying to access first, it indexes an

object from the car's array, but it returns a copy of it.

Ultimately, the letter keeps your field safe.

Our field is now fully secure and private, there is no chance of it leaking access.

Once again, by following these beautiful tables, we made sure the code is strong and bulletproof.

All right, now we can remove the random variable we made.

And that's all.

In this lesson, we added a geter, the Geter get car returns, one car object at the index of your

choice.

It indexes an object from the car's array and then it returns a new copy of the object.