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The constructor is the first thing that runs when you create an object.

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Having a constructor allows us to create the object.

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And update its fields on the exact same line.

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This is a big improvement on our previous code where we created the object and then in four separate

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lines, we updated its fields.

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This looks really disorganized.

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So it stands to reason that in this lesson you will use a constructor to update an object as Fields.

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The constructor runs as soon as you create an object.

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And the purpose of a constructor is to update an object as Fields.

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Let's go through the process.

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Step one is to create a constructor that defines four parameters.

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And to make a constructor, you need to specify the level of access which tends to be public.

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The class name.

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Followed by parameters.

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In step two, you have to call the constructor while creating a new car object.

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New car creates a new object of the car class.

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And while creating the car object by passing in four arguments, you're calling the constructor that

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expects to receive four parameters, and inside of the constructor is where you should update the newly

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created objects as fields.

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And that's why.

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Step three is that the constructor must update the objects as fields.

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The key word.

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This refers to the current object.

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The purpose of this is to distinguish between fields and parameters.

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You'll notice here that the parameters have the exact same name as the object as Fields.

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So we can use the this keyword to refer to the current object, the object that called the constructor.

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And it follows that this make refers to the field in that object.

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And we can set that field equal to the make parameter.

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In turn, we can set every field equal to the parameter that was passed in.

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And that's all.

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Once the constructor is done updating the objects as fields, the object has been fully initialized

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and our variable will store a reference to it.

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All right, let's put all of this into code.

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Step one was to create a constructor that defines four parameters.

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The constructor will be public and the constructor will get called whenever we create objects of the

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car class.

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And whenever the constructor gets called, it's going to expect for parameters to be passed in.

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It's going to expect a make a price.

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A year.

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And a color.

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Step two is to call the constructor while creating a new car object.

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So now that we've created our own constructor, Java is going to expect us to call it after we create

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a new car object.

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And we can call the constructor by passing in an equal number of arguments.

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We will pass any make of Nissan a price of 10,000 a year of 2020 and a colour of green.

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And now, instead of updating, the object is fields in four separate lines.

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The constructor is going to do it in a single line.

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And do the same thing over here.

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After we create a new object of the car class, we want the constructor that expects four parameters

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to get called.

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So here we're going to pass in four values Dodge 11,000, 2019, and Blue.

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And now, instead of updating, the object is fields in four separate lines.

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The constructor is going to do it in a single line.

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Looking good.

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And now step three is for the constructor to update the objects as fields.

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Every object that we define from the car class, it's going to have a field that matches a parameter

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in the constructor.

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So what we can do to distinguish between them is say this.

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So this refers to the current object that's calling this constructor, which means that this make refers

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to the field in that object.

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And here we can set the current objects as field equal to them.

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Make that gets passed in here, we can set the current object price field equal to the price value that

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gets passed in here.

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We can set the current objects year field equal to the year of value that gets passed in, and here

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we can set the current object as color field.

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Equal to the color value that we pass into our constructor.

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And that's really it.

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Whenever we create a new object of the car class, the constructor that expects to receive four values

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is going to get called, and it's going to update every single field in that object.

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This is looking really good.

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Let us visualize the runtime to see this in action.

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So here we're creating a new object of the car class.

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If I press a step inside, it's going to step inside the constructor that expects to receive four values.

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The make is a Nissan.

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The price is 10,000.

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The year is 2020 and the color is green.

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You can also visualize the parameter values over here.

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This points to the current object that we just created the new car object.

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By default, all of the fields start at zero or null.

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So inside the constructor we set every single field inside of the current object equal to a parameter.

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The start make equals make.

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This price equals the price value that we passed in.

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This year equals the year value that we passed in.

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And this color equals the color value that we passed in.

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All right.

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Once the constructor is done updating the object to Fields, the object has been fully initialized.

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So now our variable Nissan is going to store a reference to it.

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And now here, once again, we're creating a new object of the car class.

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If I press step into, it's going to step inside the constructor that expects to receive four values.

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This refers to the current object that we just created.

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Here we can see the parameter values that were passed in.

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Here we're setting this make the current objects is make field equal to the make value that we passed

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in Dodge.

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Here.

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We're setting the price field of the current object.

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This price equal to the price that we passed in 11,000.

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Here we're setting the year field of the current object this year equal to the year value that we passed

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in.

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And here we're setting the color field of the current object.

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Equal to the color that was passed in blue.

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And once the constructor is done updating the current objects as fields, now the object has been fully

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initialized and our dodge variable will store a reference to that object.

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So now we've got two variables.

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Each variable stores a reference that points to a brand new object.

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And here we can print the field values of each object.

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So our Nissan has a make of Nissan, a price of 10,000 a year of 2020 and a color of green.

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That is exactly what should reflect in our print function.

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Here we print every single field of the object that our Dodge variable points to.

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So this object is going to have a make of dodge, a color of blue, a price of 11,000 and a year of

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2019.

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And that's really it in this lesson.

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You used a constructor to update an object's fields.

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New car creates a new object of the car class.

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By passing in four values, we called the constructor that expects to receive four parameters.

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This points to the current object, the newly created object that called the constructor.

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So this dot make refers to the field in that object and we can set that field equal to the make parameter.

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And we can set each field in the current object equal to the parameter that was passed in.

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And that's really it.

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Once the constructor is done updating the object as fields, the object has been fully initialized and

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our variable will store a reference to it.