Inheritance Doubt

[Timothy Sam]

Hi guys, I was experimenting earlier. Why is it that we are allowed to redefine another member of the same type and name of that in an abstract class?

public abstract class A
{
int i;

public int getI()
{
return i;
}
}

class B extends A
{
int i;

public int getI()
{
return i;
}
}


What happens here? Whose i gets returned?

[Ernest Friedman-Hill]

This is called "shadowing" a variable, and it's a very bad practice; confusing things can happen. In particular, calling B.getI() will return B's copy of "i", but calling super.getI() in class B will return A's version of "i". Worse, any methods in A that use "i" will continue to use A's copy of "i", while any methods in B that use "i" will use B's copy. This could lead to subtle and hard-to-find bugs.

[Ilja Preuss]

IDE's like Eclipse can be configured to raise warnings or even compile time errors for such code.