abstract class inplementing an interface
Yuva Raj Sah
Greenhorn
Posts: 6
posted 13 years ago
I am a bit confused with the following code
******************************************
interface I1{
public int methodA(int a);
}
abstract class example implements I1{
//public int methodA(int a){
//return a;
//}
public static int methodC(){
return 1;
}
public static void main(String[] args){
System.out.println(methodC());
}
abstract void methodB(int a);
}
*****************************************
I thought the code should not compile as the abstract class is not implementing the interface method. But the code compiles and the output is 1.
Any explanation!!!
******************************************
interface I1{
public int methodA(int a);
}
abstract class example implements I1{
//public int methodA(int a){
//return a;
//}
public static int methodC(){
return 1;
}
public static void main(String[] args){
System.out.println(methodC());
}
abstract void methodB(int a);
}
*****************************************
I thought the code should not compile as the abstract class is not implementing the interface method. But the code compiles and the output is 1.
Any explanation!!!
C. Nimo
Ranch Hand
Posts: 82
Jeroen Wenting
Ranch Hand
Posts: 5093
posted 13 years ago
K&B page 133 states clearly "An abstract implementing class does not have to implement the interface methods (but the first concrete subclass must)".
Inheriting (abstract) methods from an interface is no different than inheriting them from an abstract baseclass.
In either case you must either implement them and/or mark your own class as abstract (in case you wish to possibly defer implementation to your own subclasses).
Inheriting (abstract) methods from an interface is no different than inheriting them from an abstract baseclass.
In either case you must either implement them and/or mark your own class as abstract (in case you wish to possibly defer implementation to your own subclasses).
42
Gauri Savanur
Greenhorn
Posts: 9
posted 13 years ago
The code seems to be perfectly legal.
Because if u are not implementing the method of the interface in the implementing class then u have to declare it abstract. Since the implementing class is declared as abstract it will compile.
The code will also run and give the output 1 because abstract class can be run as a standalone program. Just u can't create instance of it. Trying to create the instance will give u compilation error.
Because if u are not implementing the method of the interface in the implementing class then u have to declare it abstract. Since the implementing class is declared as abstract it will compile.
The code will also run and give the output 1 because abstract class can be run as a standalone program. Just u can't create instance of it. Trying to create the instance will give u compilation error.
