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So Djala API and how they are arranged in two packages Next to know is how do we access the classes

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in those packages so that we can use them in our own classes.

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It's not just about standard Java API or some third party API but almost all projects will generally

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include one or more packages unless we are writing some really small programs.

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So we need to know how to access classes and packages.

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And that's what we're going to learn now.

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At the end of the lesson there'll also be a demo of most of the stuff we have learned in this lesson

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.

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It is very common for classes within the package to access other classes in the same package in such

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cases classes can directly reference those other classes by just using their class names.

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But if we have to access a class from a different package then there are two ways to do it.

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Firstborn is by using an import statement.

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And second is by using a fully qualified blastin a fully qualified class name is nothing with the package

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name followed by a dot which is then followed by the class name.

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Normally we always use an import statement.

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But there are certain special scenarios where you may have to use the fully qualified class name in

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this lesson apart from looking at importunate men.

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We will also look at the scenarios when we would have to use fully qualified Glaston also know that

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these methods are used regardless of whether or not the package belongs to an external API that is even

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if a package was written by us in our own project we would still use these methods to access the classes

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in that package.

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Hustle let's look at import statement using a simple example.

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Let we look at the fully qualified placename approach.

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Let's say we want to use a class called idlest which is part of the job Rodarte you do package this

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we can use an import statement as shown here.

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That is a statement involves the key word import followed by a fully qualified name of the class which

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is most a package name Jawad article followed by a dot which is then followed by the class name.

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Idlest this informs the compiler that we want to use the class ironist from the package.

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Tarkington.

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Not that the statement must be at the top of the class outside the class definition having it inside

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a class definition or after class definition is invalid.

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So once we have the import statement in place we can use our list anywhere in the class as you can see

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we are creating an idealist object that in the method foo had we not included the import statement this

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statement would have given a compiler error.

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In the example we just saw re-imported a single class called ironist from the package Jawad Arterton

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the import statement used is referred to as an explicit import which is also referred to as single type

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import single type imports such as that we are importing a single type and that type can be either a

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class or an interface.

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An interface that will be discussed later but often you also put multiple courses from the same package

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.

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In that case there are two options.

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One is of course to have an explicit import statement for each class to be imported.

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The second option is to use something called starting work which is also referred to as input on demand

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.

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Get started work start import you would simply include an asterisk following the package.

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And this will import all the classes in the package in this example all the classes in Java that do

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package are imported on Hence the class having the statement can use any of those classes so start import

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a shortcut for importing multiple classes as you were having just a single import statement instead

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of a separate explicit import statement for each class that you want to import.

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If you're familiar with SU Well you know that we use select start statement to fetch all the data in

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that table.

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So use of stored in this case is analogous to that as we are importing all the classes in a package

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splatters multiple classes from the same package we need to use either start import or expensive imports

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.

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So one question would be Is there any recommendation among the two options one issue it's not important

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that it can break your record in future.

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Let's look at an example.

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Here we're doing a star import on book jot or tittle and our school packages.

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And we're also using a date us nobody out there to tell Angella that the school have their day class

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.

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But for the sake of this discussion let's just assume that when this was written only to tell her that

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that class so the class that we are seeing here would come from Jowler that you didn't package we can

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assume that this court also uses some other classes from Jawa not a secure package.

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And that is for the sake of just it's port not it's after a year or so it did.

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Classes introduced in dowered obscure package.

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Let's say it was introduced in a newer version of July IPA Nova that when we re compiled this could

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we get a compiler at all places where data is used that's because compiler is confused as to which declasse

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to use that is whether it has to use the Washington Gelada do art of motion and Jawa not a screen but

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using explicit import for the did class in general that Rudel package how can you go into this situation

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.

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That it's adding that the SBA wouldn't have had any effect at all.

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But this is most likely a pretty corner Nargis that at one stage of explicit import is that it adds

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more clarity that is just by looking at the import statements.

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One can tell what courses are being used in that class but start imports.

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This will be a very tedious task as you would have to skandha and darkness although there is no strict

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consensus most people seem to prefer explicit imports for the above two reasons.

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Personally I also prefer explicit inboards as I mentioned earlier an alternate doable using an import

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statement is to use a fully qualified name of the class that is you would have to do this to create

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an artist or object.

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So the fully qualified name includes the package name and we are using it on either side of the assignment

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.

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And that's just plain cumbersome.

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So it is obvious that we should use an import statement however there can be scenarios where you would

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be forced to use a fully qualified name.

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For example let's say we want to use both jot or tittle Dogget that I enjoy or killed or dead in the

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same class.

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This is a fairly uncommon scenario.

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But in this case you would have to use a fully qualified name for at least one of the classes there

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are solutions for this case.

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And if you're both of them in fossilisation you can use only one explicit Imber.

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And here is an example we are explicitly importing.

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You do.

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So when we did class by simple name as in the first statement here then it would reference Jawa taught

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you to dog.

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The second statement is using a fully qualified name no fee I start in part on job at a school then

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the first statement would still reference dollar that you did.

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So basically using a simple name of the class will always reference the class from the explicit import

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so explicit import ex-president's or start import in such a scenario.

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Just note that in this example we have only two classes but even if there were say mandate classes and

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10 different packages and we want to use all of them in the same class then we can only explicitly import

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one of them and for the rest mind you don't have to use them using their fully qualified names.

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In the second solution we will use fully qualified names for broader classes.

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Also I start important Jowler daughter tell Angela that as good as it will not make any difference we

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still have to use fully qualified names as the compiler would simply be confused if he is simple names

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for the day class.

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Not that we cannot do this it will give us a compiler it makes sense because if this was allowed you

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would have to still use fully qualified names wherever data is used.

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So the only option is to use one of the two solutions we just discussed.

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That is just at least one explicit import or use only fully qualified means next is a question on whether

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there are any side effects in using import statements.

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An answer is No.

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You can have as many important statements as you want and you may never even use those classes and it

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will not have any ethnic import statement doesn't make your classes bigger.

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That is it is not going to import the byte code of the import at us so that's not going to happen.

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Similarly an import statement does not affect that runtime performance do it simply saves you from typing

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the fully qualified name of the class.

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However on your compiler core the compiler replaces the simple class names with the corresponding fully

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qualified names just not a dollar or two line package which includes classes fundamental to Java is

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imported by default.

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So you don't have to explicitly import any of the classes in this package.

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You can directly access them finally let's do some of the stuff we just learned.

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No new methods or ideas for this demo.

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We just try all different scenarios and that would be good.

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So let's get started with demo OK here we are in the basics class.

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Let's create a variable called debt off beat.

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So this is from the job interview deal package and if you compile it says cannot find the similar date

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so the compiler is unable to define this class called did that because we did not import declasse.

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So let's put an import statement here that said jobs are not so you are telling the compiler to import

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the class from the job or to do package

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but it still gives a compiler.

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And that's because this statement has been please derk wrong position.

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So right now it is within the definition of class but it needs to be on top of the class definition

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or here cannot be inside or after class definition.

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Get more so that's an import statement.

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Now let's try starting point.

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That will come into play if we want to import multiple classes from the same package.

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So let's just go ahead and

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import our A-list from the same job or you do package and this would also give a competitor because

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idlest has to be imported.

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So let's go scroll up and make this start in quarter and we are good now game so no matter art the second

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approach me said was how explicit import for both of them

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a good read that also and this is the most preferred approach for porn most of the developers so it's

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preferred over starting work.

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OK.

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So that's about import statements and that's the first way to use classes to access classes from differ

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from other packages.

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And we said the second way was to use fully qualified class needs.

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So let's try that also.

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So let me just comment that out and here let me create a new object of the class so to use fully qualified

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name that's it.

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Now combine this so it just cannot find symbole dude.

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So that's because of the fully qualified name has been used only on one side of the assignment or not

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on the other side.

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OK so it shows the error on the left side or here.

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So we need to use on either side.

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A Navi or good so that's the second approach.

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But we should use the first approach.

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The very are using an important element so that we can directly use we can use just a simple name of

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the class.

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But here if not we will have to use the entire package name on that's just plain cumbersome and we have

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to use every where where the classes used.

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So that's cumbersome.

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So that's.

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So we shouldn't be using fully qualified names.

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But we said that we will have to use fully qualified names in certain scenarios and the scenario was

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that if you want to use a class with the same name for multiple packages then you don't have a choice

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but to use at least one fully qualified class name.

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OK so let's just try out that example too.

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So let's make this back to date

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and if you remember the second one was from Joffe-Block I got a school does it's called or test date

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too.

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So we want to use that date class from both the packages.

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So one of them is a fully qualified name and here for the other one we are using an exploit an explicit

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import.

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So there is one explicit import on one fully qualified class name students compile this Henri are gone

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.

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So you said this is one of the approaches.

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Right.

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So one of them is an explicit import.

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So this particular bit is referencing is referencing the date and the arguably package.

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And this is unexpressed important.

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So that's one of the solutions and the second one is to use fully qualified names for both of them so

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we can just read more.

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Gus

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we are good.

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OK.

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And the only thing we cannot do is

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me said We cannot how you can do this we cannot import.

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But it did cost us explicitly

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you see.

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I notice a type with the same simple name is already defined by the single pipe import of data.

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So the error is here in the second in the second line of type with the same simple name is already defined

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by a single type import which means that you are already importing a class with the same name.

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So you can do it again because when we do this we are making a deliberate statement that somewhere in

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the class that the class will be used.

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OK.

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So the compiler does not allow that.

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Even if you don't use these classes anywhere and if you just how only the importunate mess you still

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will get that error.

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So we just call him or not it out and we still get the same error.

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So you can do that.

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So that's about it.

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That's smart.

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That's all we saw in this lesson.

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So you can we both explicitly import On-Star imports and we need them to access classes from some packages

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.

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And we also say that there are no side effects of having this import statements.

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So that's one thing we also search.

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So it's not going to having these statements will not make your classified larger.

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So we discuss that.

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So that's important.

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That's a broader important statement.

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And thank you and happy courting