Doubt about final methods

I was reading the book "Programmer's guide to Java Certfication" by Mr Mughal.. 2nd edition. In the chapter about object oriented programming section 6.2 p235 talking about final methods,

A final method cannot be overridden because the modifier final prevents method overriding. An attempt to override a final method will result in a compile-time error. However, an abstract method requires the non-abstract subclasses to override the method, in order to provide an implementation.

Hmm.. i thought about the last sentence. What i understood is that you can over ride an abstract "final" method in order to provide an implementation.

which prompted to define a final method in an abstract class. But it would not compile.



Was that a mis-understanding on my part?

The abstract and final modifiers are mutually exclusive when applied to methods. That is, you can have one, the other, neither, but not both (or a compile-time error results).

I think you have no doubts on final method cannot override. According to Mughal, an abstract method in superclass must override in non abstract sub-class with implementation. If sub-class override without implementation then sub-class is abstract too. Take a look on followin code:

abstract class a //must be abstract coz has abstract method.
{
abstract void x(); //abstract method
}

class b extends a
//non abstract class so it must provide implementation for overriding
// method "x" in superclass "A"
{
void x() //overriding method "x" from superclass "a"
{
//with implementation
}
}

But the sub-class is abstract or non-abstract it can provide implementation for overriding method but what Mughal points out there is shown in above snippets.

Hope you understand.