Why can class implements two interfaces with generic method?

Question

There are 2 interfaces:

public interface A {
    ArrayList<Integer> all() throws ExceptionA;
}

public interface B {
    List<String> all() throws ExceptionB;
}

And there is class that implements them:

public class C implements A, B {
    @Override
    public ArrayList all() {
        return null;
    }
}

Also checked exceptions:

public class ExceptionA extends Exception {
}


public class ExceptionB extends Exception {
}

When I compile this code everything is OK. Why?

I know that in implementation we can use subtype (in this situation ArrayList is subtype of List). But I have next questions:

1. Why in implementation you can omit throws part? In interface methods there are throws parts of checked exceptions
2. Why in implementation you can omit generic type?