Re: Query regarding java Multiple Inheritance
Amit Jain wrote:
Hi All,
I am new to Java and need your views for my query.
What will be the solution for implementint two Interface in a single
class A if these interfaces I1 and I2 are written as mentioned below:
interface I1{
void method ();
long square(long i);
}
interface I2{
String method();
long squareRoot(long i);
}
class A implements I1, I2{
void method(){
System.out.println("--- Hi ----");
}
// implementation of square() and squareRoot() method
}
Above implementation of interface in class A will never complies
because of "void method();" declared in both I1 and I2.
That is not a correct statement. 'void method()' is only declared in 'I1'.
And we want the implementation of I1 and I2 in class A only.
How can we acheive this in such situations.
Your problem is that 'method()' has incompatible return types in the two
interfaces, otherwise 'A' could happily implement both.
An interface is a declaration of type. As such, it makes promises about the
public face of any implementation. A class can satisfy the promises of any
number of interfaces as long as those promises don't contradict each other.
In your example, the promise made by 'I1' for 'method()' to return 'void'
contradicts the promise in 'I2' to return 'String'. No way an implementation
can keep both promises for the same-named method.
To do what you want, you're either going to have to give the 'method()' method
compatible return types in both interfaces, or change its name in at least one
of them.
<http://java.sun.com/docs/books/jls/third_edition/html/classes.html#8.4.5>
<http://java.sun.com/docs/books/jls/third_edition/html/classes.html#8.4.8>
--
Lew