Question

there is a interface class, and an another class which implements this interface. If this interface had made as “extends Runnable”, then there is a conflict in another class which implements this interface class. Why ? how may i implement the another class which implementing interface class ?

Answer 1

In Java, an interface can extend another interface, but an interface cannot implement another interface.
You can use something like this:

YourClass implements YourInterface, Runnable { ... }

Or an alternative could be this:

YourInterface extends Runnable { ... }
YourClass implements YourInterface { ... }