What is public access specifier?

Answer 1

An Access Modifier is a key word in java that determines what level of access or visibility a particular java variable/method or class has. There are 4 basic access modifiers in java. They are:

1. Public

2. Protected

3. Default and

4. Private

Private is the most restrictive access modifier whereas public is the least restrictive. Default is the access protection you get when you do not specifically mention an access modifier to be used for a java object.

Java programming does not run by just a single piece of class that has the whole functionality. You have hundreds of classes that interact with one another, passing data between them and returning output to the user of the system. So it is very important for members of one class to access members of another. Here members may refer to variables, methods and even classes. So, this is where the access modifiers come into picture. The modifier associated with every member of the class determines what level of visibility that member has.

Answer 2

In a class definition, the keyword "public:" denotes that all the following members (both variables and methods) are accessible to all consumers of the class. The access specifier remains in force until another access specifier is encountered, however the same specifier may be repeated throughout the definition, and they may appear in any order.

Note that a class always has full access to all of its own members, regardless of the access specifiers. However, class members may be public, protected or private. This determines how accessible those members are to the consumers of the class. In other words, they determine how much of the interface you expose outside of the class.

Unless otherwise specified, all class members are private. Private members are only accessible to the class itself, and friends of the class (whether those friends are entire classes, individual class methods, or individual functions).

Protected members are similar to private members, but are also accessible to derived classes.

Public members are accessible to all consumers of the class.

Answer 3

This access modifier is actually working like protectedor internal, means only accessible by the derived classes (protected), or the one within the same assembly (internal).

Personally, I have not had a chance to use protected internal. I've been asked this question many times, yet when I persisted to ask for an example of the need to use it, thus far, all the examples were needed because of design flaws. (once the flaw being corrected, there is no use of it). It could be like the public modifier being applied to a data member, it is there does not mean we should use it. (declare a data member as public violates one of the OO principles - encapsulation. Another way to look at it, you expose your bank account to public!!)

Answer 4

Protected access is the exact same as private access, but also permits access to derivatives of the class. But outside of those derivatives, the member is effectively private.

Consider the following example:

#include <iostream>

class base

{

private: // accessible to class members and to friends of the class.

int m_private;

protected: // same as private, but also accessible to derivatives

int m_protected;

public: // accessible to all

int m_public;

public: // constructor

base(){

m_public = 1; // ok

m_protected = 2; // ok

m_private = 3; // ok

}

};

class derived : public base

{

public: // constructor

derived(){

m_public = 4; // ok

m_protected = 5; // ok

m_private = 6; // access denied

}

};

int main()

{

base b;

b.m_public = 7; // ok

b.m_protected = 8; // access denied

b.m_private = 9; // access denied

derived d;

d.m_public = 10; // ok

d.m_protected = 11; // access denied

d.m_private = 12; // access denied

return( 0 );

}

As you can see, derived has access to all but the private members of base. However, main, which is outside of both classes, only has access to the public members.

Answer 5

The protected access specifier means that the member data or method can only be accessed from within the class, or from within a class that derives the class.