I can't understand how multiple inheritance is achieved using iterfaces when we have to implement the abstract method ourselves?

Suppose I have

```
class A implements B,C{

public void B()
{//method of interface B implemented}

public void C()
{//method of interface C implemented}
}

```

We can just do this

```
class A{

public void B()
{//method of interface B implemented}

public void C()
{//method of interface C implemented}
}

```

I don't get how is it useful if we are not getting readymade methods, in what situations and how is this useful? Can someone please explain with an example? Thanks !!