Java Essentials - Access specifiers in java

Access specifiers in Java. Using this access specifiers we can define the access scope or the

accessibility of different data members and member functions of a class. We are having four

different types of access specifiers in Java. So let us discuss one by one. So what are the

access specifiers? Access specifiers or modifiers are used to define the scope or

accessibility of a data member or the member methods of a class so whether this

member method will be accessible from this scope or not whether a member method

or the variable rather will be used from this particular scope or not that will

be decided by this access specifiers there are four kinds of access

specifiers available in Java the first one we're going to discuss there is

a private so from the very keyword private you can get the idea that

private members are accessible only from the class body default a default

member can be accessed only from the same package obviously from the class body

and also from the same package protected protected members can be accessed by

the child classes only next one is a public there is a fourth one the last one

for public members the members can be accessed from any other class or object

a class from the different package can also access it so that means this public for the

public we can access this public members that is the member variables and member functions

from any class or objects a are also a class from the different package can also access

these members if the member is under the public specifiers so let me go for some practical

demonstration to give you a better idea on this access specifiers in Java in this demonstration we are discussing access

specifier just consider this one under the package access specified we having two classes two Java classes one is access specified or Java and the one is access

specifier same package or Java so two Java classes under the same package only

to show that that how the two classes can access their members if they are existing

in the same package so at first we're discussing access specifers same package

java here we're having only one class C having having having having

our public INTP that is a public member can be accessible from any class INTQ here we

haven't mentioned anything private public or protected so it is a default scope so default

variable can be accessible from any same package from any other class within the same package

so that means this queue will be accessible from access specifier Java class because it is

under the same package access specifier we'll be testing that one private INT R is

it is non-accessible from any other class because it is the private member

We're having the constructor passing three parameters to initialize three instance variables

and also we're having the display method which will display the current content of P, Q and

R instance variables. So that is our access specifers same package.java. Now we are going for

the another Java class that is our access specified. Here we have defined this public INTX. Public

members are accessible by any class and also inheritable private I and T Y private variables can be accessed only within this

class and they are not inheritable they are not getting inherited to the

derived class or subclass protected I NT Z protected member can be accessed in the

derived class also this is my this my constructor a passing three parameters

to initialize three instance variables we're having the display method which it display the current content of X Y Z instance variables now we are having

this class B which is inheriting extending the class A so what will happen public X will be

inherited here private I nt y will not be inherited protector Z will be

inrated and public display will be inherited here so now what we are doing here we are having the respective constructor passing three parameters so from constructor of

B set member values of class A so we are calling the best class constructor the

best class constructor will be used can be called using the super keyword so

super A comma B comma C so what will happen this A comma B comma C will be assigned to this

I n T A I nt B I nt C to initialize the instance variable of the class A we're having the display method

here which will display the value of X and Z why the value of X and Z only

because X was under the public scope and Z was under the protected scope so

they were only got inherited private member INT Y has not got inherited in class B

so from class B Y will be unaccessible so X is public member of class A and Z

is a protected member of class A so that's why they got to inherited and they can be accessed from the display method we're having this

access specifier there is a five last class here within the main function

we have due this a line we're printing there is a data of class B so A is

the name of the class the object name is class B is equal to new B 5 10 and 15 so

whenever you are calling this class B or display let us see what is happening

in case of class B or display we are finding that X and Z values are getting

displayed why that means when the whenever you are calling this class b dot display

actually this particular display method is getting called this particular display method has got called this particular display method and that's why we

could get only this x and z values are getting printed here because this

a class a class object has got instantiated with the b class constructor so

that's why class b dot display is actually calling the b class display method next one is that we are defining another class a object

that is a class a which is getting instantiated calling the class a constructor

so class a display is actually displaying the class a display method because we are getting both x y and z values are getting printed so that means this particular display method has got called and that why the x y and z

values have got printed accordingly now we are dealing with the class c c class i told you that it

it was defined within the access specifiers same package java which is another class within the same

package i told you this one earlier they are in the same package now what is happening so

class c is the object is a new see that is constructed you are calling now you are

calling this display we are calling this display what is happening you are finding

that 316 25 3 16 25 is getting printed because actually this particular

method display method is printing p2 values so using this constructor this

pqal values have got updated has got initialized so respective values have got

printed we know that public member variable p and the default scope

variable that is a Q they are accessible from other classes defined within the same

package so what will happen you can find that this class c dot p and class c

they have got initialized with this 9 and 56 so p and q they have got initialized with 9

and 56 r is not accessible from the outside of the class so you are not trying to

initialize this class c dot r so now what will happen if i type class c dot r you see

Class C is the respective you see R is not there there is no R so it is not accessible

So after initializing them if I go for the display method you can find that this 316 have got updated with 9 56 and then R is still with the value 25 so 25 was still there

So the class C dot display is printing 956 and 255 for the respective values for for the respective values for our PQ and R

So in this way we have discussed that how this access specified is playing of such a very wider role in our Java code and you have explained and demonstrated with the proper examples to clear your doubts and to give you more clarity on this subject

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