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Инкапсуляция
джава
ява
сеттеры
геттеры
java для начинающих
Encapsulation (Programming Language Paradigm)
Programming Language (Software Genre)
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  • ruRussian
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00:00:02
about methods, we learned how to create,
00:00:05
how to return a value and how to
00:00:09
pass arguments to them, and in this lesson
00:00:11
we know about encapsulation, what it is
00:00:13
and why it is needed, we have a class of songs
00:00:17
from previous lessons and we have a class of
00:00:19
another cool object in which the
00:00:23
main method we create an object of the song class and
00:00:25
pass these values ​​to the fields and what’s
00:00:31
bad about this program
00:00:32
and what’s bad is what we pass, we access the
00:00:35
fields of this class through a dot, that is, we
00:00:38
directly access these fields
00:00:42
now I’ll try to demonstrate
00:00:44
the shortcomings of this approach, imagine
00:00:47
that you are programmers, you are writing a large
00:00:49
program that will be used by the
00:00:51
end user,
00:00:52
not a programmer, an ordinary person, and
00:00:55
imagine that this class, that is, this is
00:00:58
your program that you
00:01:00
wrote, and here the
00:01:04
end user accesses your created
00:01:07
class and uses it in some way So,
00:01:10
what is the disadvantage, what is the disadvantage of
00:01:13
directly accessing your fields, but the fact is
00:01:15
that all the same, these fields should be
00:01:20
hidden from the user because you are
00:01:23
carrying out some actions with them inside the
00:01:24
class and this data should be for
00:01:30
internal use, why because
00:01:33
that for example you may want to change
00:01:35
your name in a field because you
00:01:39
needed to
00:01:41
do it in the internal work of the class, but
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at the same time your end user will
00:01:48
no longer be able to use this field
00:01:51
because if you change, for example here,
00:01:53
logically the class no longer fits
00:01:56
my name the name user is suitable for you, for example,
00:01:59
if you do this, then your user will
00:02:02
not be able to use this field,
00:02:07
another example, for example, your user is
00:02:11
not a very smart person and he wants to
00:02:14
set an empty name,
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so for this class to work, you are asked to
00:02:21
you need a non-empty name and you
00:02:23
naturally need some positive is also
00:02:25
not empty positive is not empty
00:02:27
numeric value for age your
00:02:30
user sets empty exactly example
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empty name and sets negative
00:02:36
age to straight minus five years if you
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run this program let's
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run here we will output red. speak
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if we allow this that that everything will
00:02:52
work that is, there is no name there is a
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negative age but the program
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works and it works again and the warmth
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and reason that the user can
00:03:02
directly access the fields of the class
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what would we do if he accessed not
00:03:09
directly but through methods in these methods we
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could place a check that is,
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before we assign a value to these fields
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we in these methods methods
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check and either positive years
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values ​​if we are talking about age or
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not empty years and value if we are talking
00:03:27
about about the name and these are the methods in which
00:03:30
we check that these methods serve as
00:03:36
such a layer between your fields and
00:03:40
between end users, these methods
00:03:42
are called guitar setters and now we
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will create them
00:03:46
in general c3 guitars this is a standard
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agreement and they are used in any
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type of this
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application this is a public interface in my opinion in
00:03:59
general, in simple words then five
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is the interface through which the
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user gets access to
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the functionality of the program and the user does not
00:04:09
need to know how everything works inside
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the user, you should only give
00:04:13
some kind of interface through which he can
00:04:16
get the necessary functionality and the
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user should not touch the
00:04:20
internal structure of the program the
00:04:22
name for this is we we don’t give the user
00:04:26
access to the variables themselves, the fields of the
00:04:28
class modem access only to the public
00:04:31
method, so let’s make these fields
00:04:34
break through rule this
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keyword which means that this field is
00:04:42
accessible and visible only within this
00:04:46
class and you see that as soon as we
00:04:48
made the
00:04:51
name variable they rule,
00:04:54
since it has already ceased to be available in
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other classes, that is, if you put a
00:05:00
keyword about it in front of your field
00:05:02
in the class, then this field is now
00:05:05
available only within this class,
00:05:08
in particular within the class of persons
00:05:11
within this class, and
00:05:12
you see we can use
00:05:14
change and use this change,
00:05:16
but in other classes we cannot do this;
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if we hover, we will see
00:05:21
the error name has provide access in asks,
00:05:26
that is, to configure it and we
00:05:28
cannot use it in these we also make the
00:05:31
right about it and which provide and you will see
00:05:36
that now we cannot use and
00:05:37
bake so now the user of course
00:05:40
cannot get direct access to
00:05:41
the fields so we can erase this how
00:05:47
now the user will
00:05:49
access these fields how will he
00:05:51
assign them how will he receive the
00:05:53
value he will receive the value
00:05:56
through a sieve and leggings for this, let's
00:06:01
first make a garden arbiter for the name
00:06:05
and then make it for age for this
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we write public white hearty parameters
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we write string name string let it be
00:06:23
lake and here we equate our
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field to this value that came
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in our time parameters equals username
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now based on us can
00:06:45
assign a
00:06:46
name using this method by passing a
00:06:50
string to the parameters and in this method we
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assign this field a string
00:07:00
passed passed their parameter and
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pay attention to the fact that our method is
00:07:05
white because it does not return anything
00:07:07
only assigns but another get method
00:07:11
we will have with a return type of
00:07:15
string because it will
00:07:17
return a string
00:07:19
public string drinks name with name empty
00:07:23
parameters
00:07:27
when calling this method we will have a
00:07:30
string returned
00:07:31
which is a field in this class
00:07:35
let's do the same methods for the field
00:07:39
and public would set ych
00:07:45
here in the parameters we now have no
00:07:48
string but int int user speech here also
00:07:55
needs to be done so user speech and in the
00:08:01
method we have ych equals user speech
00:08:08
again howls here int and method public
00:08:14
int int and because we will return
00:08:18
an integer with a numeric value
00:08:21
public and get rich [ __ ]
00:08:28
we have four methods in each of them
00:08:30
means
00:08:32
in each and here is a pair of
00:08:35
methods a pair of methods intended for
00:08:38
this field and a pair of methods
00:08:40
intended for 2 fields now in
00:08:42
another class
00:08:44
we can access these fields through
00:08:48
these methods and let's try again.
00:08:58
set name some name
00:09:03
ps one one .
00:09:07
set h any number and ps one
00:09:13
that speak we will return call a method
00:09:17
that will greet us three times
00:09:19
and give out the age and
00:09:22
you will see that we first managed to get a name
00:09:27
and we got
00:09:31
the age set using these methods
00:09:34
we can also return name and age
00:09:38
using their corresponding
00:09:39
tagged methods one .
00:09:43
get rich and let's write here that
00:09:47
we will display the first ones on the screen and write
00:09:49
that
00:09:53
we will display the value in my method
00:10:01
so and so
00:10:09
and here we do the same thing, let
00:10:23
's run
00:10:28
on with the help of Hitlers those
00:10:31
variables that we assigned with
00:10:33
the help of sidors with the help of guitars we they
00:10:35
were brought out in another class, what is the advantage of
00:10:40
this approach, but the fact is that now we
00:10:43
can, for example,
00:10:44
inside the class, we can change the name of dreams for
00:10:48
him, for example, to whatever I want, to I
00:10:50
don’t know, login, for example, any name,
00:10:56
and here users will no longer notice
00:10:58
this because inside of this class in the
00:11:00
methods we will simply change the internal
00:11:04
logic of the internal logic of our class and
00:11:06
you see that nothing has changed for the user,
00:11:09
he accesses this
00:11:12
internal variable using the same
00:11:14
class, but the internal variable can
00:11:17
change in any way if we run something like this and
00:11:20
so we change the login inside
00:11:26
class one more variable and lower it and
00:11:32
you will see that nothing has changed besides
00:11:38
this, we can in these methods in satires
00:11:40
we can check the correctness of
00:11:44
the water, that is, for example, our
00:11:49
user cannot have an empty name
00:11:50
because the person must have a non-
00:11:52
empty name for this, we check
00:11:55
the username here
00:11:56
let's return it back to them there are already
00:11:58
aunts on them more logically name is we also do
00:12:04
n’t know and here we will check if it is not
00:12:12
empty or the user has provided us with a
00:12:14
name at the input for this we will call the
00:12:18
is empty method which is available with
00:12:21
string and we will return this method
00:12:23
true if our line is empty I
00:12:28
returns falls if the line is not empty
00:12:32
therefore if user is empty we print the
00:12:35
error you entered an empty name body
00:12:40
my name is els otherwise els
00:12:47
we assign the user username so here we have a
00:12:53
fuser name is empty so here we write
00:13:00
and now our user
00:13:04
will not be able to set an empty name because in the
00:13:07
center we encapsulate the necessary logic
00:13:12
that has checked that will check the
00:13:14
correctness of the water and let's
00:13:18
do the same for set it if you zerohedge that
00:13:24
is, the age that was submitted is
00:13:25
greater than zero, strictly no longer possible, then
00:13:30
we assign not let's do if
00:13:33
less than zero then we display an error then we display an
00:13:38
error we write south
00:13:45
incorrect so age must be
00:13:48
age must be positive els
00:13:54
assign age if we
00:13:58
run it now nothing will change let's
00:14:01
stop calling this speak and
00:14:05
call it like this they see name and
00:14:09
+ online everything is acceptable nothing
00:14:18
the same name has not changed, the same age,
00:14:21
but if we now try to assign an
00:14:28
empty name and run it, then first of all
00:14:34
our program will give an error and you
00:14:41
see what it means here that the
00:14:43
name variable is not I did not assign
00:14:47
the value that was supplied,
00:14:49
we will do the same thing with age, if we set an
00:14:51
empty age, or rather empty and
00:14:53
negative, then our program will display a
00:15:02
message that the age must be
00:15:04
positive on this main day
00:15:07
of surrender
00:15:08
once again, you must
00:15:10
limit your fields as much as possible from other classes,
00:15:13
that is, you must do so that, if
00:15:15
possible, your fields were visible
00:15:18
only within one class of the class in
00:15:21
which these fields are
00:15:24
declared and you must access these fields
00:15:27
through a
00:15:28
setter
00:15:29
and through getters

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МОЙ НОВЫЙ КУРС: https://www.youtube.com/watch?v=rRe1vT0SDD8 ПРАКТИКА НА JAVA: https://java-marathon.tilda.ws/ Реклама и сотрудничество: [email protected]

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