does inheritance break the encapsulation or data hiding?

[Anil Deshpande]

This is a conceptual person.

Say I have Class1(with private method1) and Class2 extending Class1 and tries to override. And Conceptually you can't override private method. Because private methods are basically not inherited and thus can not be overridden.

The code looks like this

   
class Class1
{
	private void method1()
	{
		
	}
}

class Class2 extends Class1
{
        //THIS IS METHOD OVERRDING, WHICH DOESN'T WORK. ITS JUST A NEW METHOD DEFINITION. ITS NOT METHOD OVERRIDING

	public void method1() {
		
	}
}
 

But Now looks at this code

class Class1
{
	private int a;
	
	public Class1() {
		
	}
	
	public Class1(int a)
	{
		this.a=a;
	}

	public int getA() {
		return a;
	}
	
	
	
}

class Class2 extends Class1
{
	private int b;
	
	public Class2() {
		// TODO Auto-generated constructor stub
	}
	Class2(int a, int b)
	{
		super(a);
		this.b=b;
	}
	public int getB() {
		return b;
	}
	
	
}
public class TestClasses {
	
	public static void main(String[] args) {
		Class2 class2=new Class2(10,20);
		System.out.println(class2.getA());//HOW class2 has "a" as instance variable. It's private and getA() should create a problem
		System.out.println(class2.getB());
	}

}
 

HOW class2 has "a" as instance variable. It's private and getA() should create a problem?

But it works perfectly fine. Its prints the value of a as 10. How come Class2 for access to "a" even though its private instance variable of its super class Class1.

Isn't it against the object orientation?

does inheritance break the encapsulation or data hiding?

OR AM I MISSING SOME THING

[Bert Wilkinson]

Yes.....You are missing something.

When you extend a class, you are extending all the methods in that class as well. So, any object of type Class2 in your example has full access to anything that an object of Class1 would have. So, in your example, your class2 object behaves as if it is a member of both Class1 and Class2, because it extends Class1.

This is the clear definition of inheritance, and does not break encapsulation rules.

[shivendra tripathi]

You are calling a method which you have declared as public. Try doing new Class1.a inside TestClass you will get error. Now modify the access modifier of a as public and try Class1.a it will work.

[Jim Hoglund]

Class1 is well encapsulated if all its member variables are declared
private, so they can be accessed or changed only by method calls.

Regarding your first sample code, a child class inherits all the parent
member variables and methods that it can see; those with public,
protected and often package access. In this case, Class2 cannot see
method1() of its parent, so Class2 is free to define a similar method.
As you said, this is not an example of overriding.

Jim ... ...

[Anil Deshpande]

Thanks a lot for the replies.