abstract method

[itisha jain]

"A subclass of a class with an abtract method must provide n implementation for the abstract method".

The statement is given as false in khalid mughal.the explanation being...

Abstract methods foma superclass need not be implemented by a subclass.The subclass must then b declared abstract.

however,i thought the statement is true.Plz explain

[Lalitha Gottumukkula]

Hope an example makes the point clearer.....

abstract class A {
abstract void method1();
}
 
// notice, the following class is not implementing method1(), but marked abstract
// if you remove abstract, compilation fails in the below line
abstract class B extends A {
    void method2() { 
System.out.println("in B : method2()");
}
}  

[A Kumar]

HI,


Have a look ...

  
abstract class AbstractWithMain {
 
     public abstract void test();
}
 

abstract class AbstractWithMainXtendss extends AbstractWithMain{
 
    public abstract void test();
}
 
public class AbstractWithMainXtends extends AbstractWithMainXtendss {
 
    public  void test(){
        
    }
    
}
 

 

[Akshay Kiran]

This should make it clearer

abstract class Abstract{
// A class with an abstract method
abstract void doThis();

}

abstract class A extends Abstract{
// extends abstract but provides no implementation, and hence decld. abstract

}

class B extends Abstract{
// B extends Abstract, but provides no implementation AND is NOT abstract
// The compiler throws an error

}

Therefore, a subclass of a class with an abstract method must either be declared abstract or must provide an implementation of the abstract method.
I put that phrase in bold because, it is only true for classes that have abstract methods, and not necessarily abstract classes in general.

abstract class A{
void someMethod(){}
}

class B extends A{
// not abstract, doesn't override the someMethod of A
// no problem
}