Java sort object by list type property

Question

I have the following objects:

public class Shipping {
    String name;
    List methods;
}

public class Method {
    String serviceType;
    Strin         


        

Answer 1

We will assume all the shippings have at least 1 method. So you want the methods of the shippings to be sorted by cost. So let's do that:

shippings.forEach(shipping -> {
    shipping.getMethods().sort(Comparator.comparing(Method::getCost));
});

Then you want the list of shippings to be sorted by the lowest cost of their methods. The lowest cost is the cost of the first method, since they're now sorted:

shippings.sort(Comparator.comparing(shipping -> shipping.getMethods().get(0).getCost()));

Note that this assumes that you want the costs to be compared lexicographically. If, as I suspect, the cost is in fact a number, then it should be stored as such in the Method class, and not as a String. So make it an Integer or a BigDecimal, or whatever the appropriate type is.