what is the actual use of interface in java? [duplicate]

Answer 1

What you like : thousands of abstract methods in one Abstract Class and inherit this class OR make as many interfaces for specific abstract methods and use those only you want by inheriting as many interfaces as needed...

abstract class A
{
 //thousands of abstract method();
 abstract methodA();
 abstract methodB();
 abstract methodC();
}

//OR
interface ForOnlymethodA
{
 void methodA();
}
interface FormethodBandmethodC
{
 void methodB();
 void methodC();
}

So, use that method only what you just need by inheriting particular interface, if you are inheriting Abstract classes then you are unnecessarily inheriting all methods that you don't need in one class and may be needed in some other classes..