public RoutingTableSpec setHop(int i, HopSpec hop) {
        hops.set(i, hop);
        return this;
    }
Sets the hop spec at the given index.

@param i   The index at which to set the hop.
@param hop The hop to set.
@return This, to allow chaining.
messagebus/src/main/java/com/yahoo/messagebus/routing/RoutingTableSpec.java