Difference between public member and private member of a class in Java?

Answer 1

public members can be accessed from outside the class they were declared in, private members can only be accessed from within the class they were declared in. Private members are commonly manipulated through get/set methods, which allows for greater encapsulation and hides the implementation from the calling function.

Example:

class sampleClass{

private: int private_member;

public: int public_member;

public: void setPrivateMember(int x){private_member = x;}; // private members can be accessed from within the class that they are declared in

public: int getPrivateMember(){return private_member;};

};

int main()

{

sampleClass A;

A.public_member = 5; // Perfectly legal

A.private_member = 7; // Syntax error, this will not compile

A.setPrivateMember(7); // Legal

cout << A.getPrivateMember(); // Legal

return 0;

}

Answer 2

A public member may be accessed by any class. A private member may only be accessed by the class in which it is contained.

Example:

// class A contains both a public int and a private int

class A {

public int publicNumber = 0;

private int privateNumber = 0;

}

// class B will attempt to access the members of A

class B {

void f() {

// Create a new instance of A

A a = new A();

// Try to print out each member

System.out.println(a.publicNumber);

System.out.println(a.privateNumber);

}

}

If you put each of these classes in a separate file and attempted to compile them, you would get an error informing you that 'privateNumber has private access in A'

Answer 3

A class member is simply the definition of a member, whether that member is a member variable or a member method. An instance member is the realisation of that definition, just as an object is an instance of a class.

Answer 4

The keyword private for the class is meant to be private to the class declare it. The private for the member is for the class contains that definition.

So the answer is a private class may have public, protected and private members.

Answer 5

That depends on whether you mean a member variable or a member method. A class member variable is the definition of a type within a class. A class member method is the definition of a function within a class. You should know that objects are instances of a class, but each object has its own discrete set of member variables (including those inherited from base classes), each of which is an instance of the member variables defined by the class of the object, including its base classes. Member methods are different insofar as there is only one instance of each method per class, regardless of the number of objects instantiated from that class. Bear in mind that the entire concept of OOP is an abstraction to aid programming, so its easier to think that every object actually has its own discrete set of methods, when in fact they don't. They are really no different to structures and functions that act upon those structures, but the OOP concept ensures we don't call functions upon structures that have no business operating on those structures.

Answer 6

Private members are only accessible to the class itself and friends of the class.

Answer 7

Private means that the member can only be accessed by methods of the class, while public means that any code that has an instance of the class can access the member.