Re: Query regarding java Multiple Inheritance

From:

Patricia Shanahan <pats@acm.org>

Newsgroups:

comp.lang.java.programmer

Date:

Sat, 28 Nov 2009 01:19:08 -0800

Message-ID:

<FPOdnQR_9pSUdo3WnZ2dnUVZ_hmdnZ2d@earthlink.com>

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. And we want
the implementation of I1 and I2 in class A only. How can we acheive
this in such situations.

The solution is to design so as to avoid having a single class implement
two incompatible interfaces.

There are some interfaces that can be combined, because they are
well-known and have method names that are unlikely to be duplicated. For
example, compareTo is unlikely to be used in any interface in a way that
is incompatible with its declaration in Comparable.

Of course, it could be avoided by defining A to have a method returning
an object that implements an interface, rather than directly
implementing the interface.

Have you encountered this as a real problem? It does not seem to happen
very often.

Patricia