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Not let's look at method or writing we brief Your discuss method or writing while introducing inheritance

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and it was part of the final design of a work history which is reproduced here here posted a behemoth

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third in the staff class is actually writing Posture Review method and end a.

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That is the operating method must have the same name deposited if you met that in the User class.

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Well posted have you but the review needs to be approved by an editor.

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We know that but the posted of you mattered in the staff class does not need any approval.

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And so the overriding behavior is not needing any approval.

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So then a regular user review than the Bush and the user classes invoke.

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But if any of the staff members post a review then the posted of you there in the Stav classes invoked

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in their democracy Gram's which we are protesting polymorphous on.

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We did use both user unstaffed classes on both hardballs state of New Method.

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So we already implemented Metro are we.

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But there are some rules associated with method overriding and we will learn those rules.

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So method or what rating writing what we are doing is redefining the behavior off the method in the

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superclass and it could mean few things one of them is defining new behavior.

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That is the overriding method does something different which is specific to sapless And another thing

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can be to extend the behavior of the superclass method.

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That is you would do what you want the superclass method does.

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And then you would do something more.

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Finally method of writing can also be used to provide better implementation.

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For example the superclass method might belong to some third party library and it may have been written

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very efficiently.

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Now since it is a library card you don't have any control over the source.

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So you can write a new class with a brand new method that overrides this inefficiently read and method

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.

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So the numerator would how much more efficient implementation.

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Not in order to superclass defines a contract through its methods and consequently define a common protocol

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for all x subtypes.

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So when you order an item a third in the superclass you are agreeing to fulfill the contract.

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That is you're telling the outside world that the only one writing method looks exactly like the order

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didn't matter matter or writing in words.

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Couple of rules that are based on this notion of fulfilling the contract.

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In addition to having the same letter name there are two rules.

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What method are writing to work.

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Let's see what those rules are rules is if there are any method parameters.

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Then they must be seen.

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In addition the return types must be comparable and the second rule is that the overriding method can

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be less accessible.

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Let's not look at both these rules in some more detail.

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In the first rule the fusspot which says that the method parameters must be same is straightforward

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as the overriding mother should look exactly like the old written method.

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The second part says that the return types must be compatible which means that the return type in the

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overriding method must be either the same written by as in the superclass method or must be a subclass

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.

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This baby abide by the contract as a subclass.

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Very true.

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Everything is superclusters as it inherits all the methods of the superclass.

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But if the Met the parameters are the same under different types are incompatible.

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Then we get a compiler error.

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No coming to the second rule it says that the alternating mudguard can be less accessible.

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It means that access level must be either same or friendlier.

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For example you cannot operate a public method and make it private.

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Doing so under a compiler.

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So those are the two rules for operating a method.

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Next let's look at something called Superguy work as an email just it can be used to access a superclass

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method from a subprocess and is typically used for extending behavior defined and superclass.

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If the method its superclass is not aware it and in the subclass then it can be either accessed directly

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using the method name as we already know or we are the super cute but typically you would directly access

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it using the simple matter only not using the Superguy word.

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But if the method in superclass is overridden I would want to access that method.

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Then you must use super keyword resort example posted a view we know is an overriding matter in the

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stuff glass circle in riposted.

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And the user class from within this method in the staff class we would have to use supercool.

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Otherwise we would be invoking the same method in the staff class could end up in an infinite loop after

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working superclass method.

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You can see that we can have some additional work thus extending the behavior that is defined in the

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superclass matter and that's how you typically extend behavior.

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Not that it is not necessary to invoke an order it doesn't matter.

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Only an overriding matter over it and method in the superclass can be invoked from any of the subclass

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methods.

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Now Superguy word is related to objects so it can be used inside a static method and you get a compiler

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error if you try to do the supect you can also be used to access something called it free which belongs

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to the superclass.

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We say that a field and supercluster is hidden.

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If the field with the same name is declared and the subclass not that it is only to be a name that matters

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here that macros to hide are free.

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Everything else like that it by access modifier started non-stock to create is in Meridian.

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If discipline's does not use Superguy won't always use a field in its own class or not Bahujan for your

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superclass.

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So that's method overriding.

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But we still have a few more concepts to cover before doing that.

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Let's first review what we learn so far in court.

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Let's begin with testing or writing rules.

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After that people look at the super keyword for this demo.

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We will continue using lower classes related to our case study that is use it or jalouse staff but Java

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and so on as we are going to test the roots.

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Let's actually begin with the second overarching goal but says that the writing method should not be

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less accessible.

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So this is standard Java and we have this method posted a you which is operating at the posted of your

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method and user class.

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So in the User class it has public access level.

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So in this stuff class also it has public.

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So let's just make it less accessible here.

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It's supposed to be either same or more friendlier but not less restrictive.

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So as you can see we get a compiler error.

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Says cannot reduce the visibility of the inherited METAR from user.

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So you cannot do that it has to be either same or more friendlier.

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So that's the second overriding rule.

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Now let's just try the first method of writing.

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And in order to do that I actually created a new class called Review and the review classes basically

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represents a review and it has two variables one is sort of your text which holds the text for the review

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and the other one is approved with a review that has been posted has been approved by an editor or not

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.

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If it is a user if it is if the review was posted by user needs to be approved by editor but if it was

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posted by a staff member it does not need any ill.

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And we know that.

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So let's just start.

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So this is a review class and the review text is initialized why this constructor and that proved reliable

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.

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We have to get it on center so since it's proved that there is.

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We know that it is an artist named as easy.

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So we saw that in our Naming Conventions does it or simply set approved.

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So it's going to set the rules.

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So in use at our job let me just but let's modify this let's introduce a new parameter here let's call

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it DOES IT review text and so on.

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Let's create a new view object.

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It's pass in the rebute text.

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It's just a view looks just great in this review.

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So the written type has to be modified.

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Here to review.

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Yes.

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So now if your object is getting created and since this is the user it's getting since the user is posting

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this.

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So if you go here and that if your text gets passed here under a broom since it does not have any value

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it gets a default or false and which means that it does not get approved.

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And that's what we need for effort.

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If they are Beuys posted by user.

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So we'll just leave it like that and let's going to add staff.

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So staff has posted have you on we want to override it.

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So let's change this review next.

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So now this method has the same parameters as the overridden matter.

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But we said that this was a compiler error because the writing method has the same name on the same

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parameter but incompatible types in the superclass it was a review.

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And here it is hard wired.

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So here if I hollowed audit the message says the return type is incompatible.

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So it needs to be a compatible return so it needs to be either review or one of its subtypes.

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So let me just change this review line.

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Let's just make this written new review so that we don't have any compilation that are supposed to review

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as now or writing the superclass method and the rules have been followed.

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So that's about overriding rules.

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Next let's does the super keyword search super key word can be used to extend the behavior.

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That is you can work a superclass method from a subclass supposed to review.

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Let's say for example from the user.

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This is what Dyster class.

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Let's say we are in Woking So we have created this type of object here.

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So staff object is here and has a reference type of user and the object type is stuff.

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And we want to call the poster of you mattered and it's just called posted of your mentor and pass an

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empty string as a review.

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So unstaffed or Java.

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So the first thing that we need to do here is let's invoke the superclass masterclasses super Dawk austerity

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view and let's pass the review text.

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Has he said of your text.

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What is whatever has been passed in this matter.

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So we have this and all you need to do now is just written this so now it's going to call the superclass

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method.

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So if you see here you just comment something on the second site says stuff posted even a user posted

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review.

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So we are invoking post-edit of your method and first the one in the subclass gets invoked here and

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the first the one in the subclause got to invoke and put in staff post a review and then we are calling

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the superclass method posted a few hundred buttons.

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The second statement when the Superquinn the poster reviewing the user classes has gone invoke.

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And that would return a review object.

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And since we are and the staff class we need to set the approved status to recruit because the one that

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is written by a user class will have on a status of fall.

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So let's just make it true.

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So it looks more realistic now.

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So that's it said if you did not use this key word then you get you end up in an infinite loop because

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you're just invoking the same post-Arab you mentored and that will give an error called stack overflow

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error.

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It's not what we want it is but main thing is that you can see you can see that it's always staff boss

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to review underdosed just invoking recursively and at some point it will throw an error called Esquire's

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and guttered and Sohmer call stack overflow error which is part of the Gelada act like package.

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So that's because we were.

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We kind of got into an infinite loop.

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So it has to be super.

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So that's one thing.

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And we also said that superclass cannot be used so perky word cannot be used in a static Minturn's sort

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of just put a start here to hide its name or does static mattered and nurses super Daut.

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Here it says cannot use super in a static context.

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So we can't use that.

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So that's gone on the last thing about superballs that can be used to invoke a hidden field.

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I actually added a field here in user class called ID which is initialized to 1 and I'm hiding it here

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in the subclass stuff here.

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I'm really declaring it here an idea is to not have this medicore print ID which is printing ID Fosdick's

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going to print ID directly by using them.

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I mean just a simple name ID on the second statement uses the super key word and it's going to user

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test.

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Not just uncommon this where we are accessing the prent ID motard sort of mirror just on this.

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So here it says for ID pins s2.

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And then for superdog ID Princesa one.

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So if I go into this material you can see that when we are accessing ID it's actually accessing the

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ID in the same class but.

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So this idea is actually hiding that Id read and the superclass.

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But when I say if I want to access the hidden food then I have to use supercooled here and that would

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access the ID free.

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So thats about it.

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So we have to start everything that we have learned so far and upset and once again I'm showing this

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an eclipse just to save some time and that's.