add element to iterable in java

Question

I have the following code:

public class Router {
  private Iterable<Route> routes;

  public Router(Iterable<Route> routes) {
    this.routes = routes;
  }
  public void addRoute(Route route) {
    routes.add(route);\\problem is here
  }
}

I highlighted the line which is not working. Here I try to add a new object to the routes. In main file routes are:

public class RouterMain 
{
    public static void main(String[] arg) throws IllegalArgumentException 
    {
        List<Route> routes = new ArrayList<Route>();
        Router router = new Router(routes);
    }
}

The task is to add an object in iterable object in Router class. As I understood Iterable can iterate, not add something. So what should I do, convert routes in Router class to a List, add an element and go back?

Answer 1

Iterable<Router> is used to enable iterating over the Router elements contained in your class. It is not a Collection, though many collections implement this interface. It doesn't have the add method. It only has a method that returns an Iterator<Router>.

You should use some Collection (List, Set, etc...) to store your routes. Those collections have add method.

public class Router {
  private List<Route> routes = new ArrayList<Route>();

  public Router(Iterable<Route> routes) {
    for (Route route : routes)
      this.routes.add(route);
  }

}