Question

i have done this so far, but having difficulty with part b. It is a mock exam paper and not sure on the rest of part b.

Q)
Sum up the elements of a sequence given by s.valAtIndex(i).
s is of type Seq.
Seq is an interface that has a method valAtIndex (integer parameter and double result).

(a) write the interface Seq.

(b) write a class Geometric, implementing Seq. so that each instance s represents a geometric series as follows
s.valAtIndex(0), s.valAtIndex(0)…
such that the ith element s.valAtIndex(i) is equal to the ith power of the base b i.e. b^i. (recall that b^0=1)

(a)

public interface Seq{

public double valAtIndex(int i);
}

(b)

public Geometric implements Seq{

Seq s;
private double b;

public Geometric(double a){

s = new Geometric(a);
this.b=a;
}

@Override
public double valAtIndex(int i){

return 0;//not sure how to do this method

}

Answer 1

You mean something like:

@Override
public double valAtIndex(int i) {
    return Math.pow(b, i);
}

?

EDIT: Also, as mentioned in other answers, remove Seq s; and the line regarding it in the constructor. What you should have at the end is:

public class Geometric implements Seq {
    private double b;

    public Geometric(double a) {
        this.b=a;
    }

    @Override
    public double valAtIndex(int i){
        return Math.pow(b, i);
    }
}