Eliminate null key from hashmap which is present inside an arraylist

Question

I am looking for an optimized solution to remove null keys from a HashMap. This HashMap is present inside an ArrayList. Please find the example below.

public class Car {
    String year;
    String model;
    Map<String,String> colors;
}

List<Car> listOfCars = new ArrayList<Car>();

Sample of the colors map could be like this:

{
   red(1),
   blue(2),
   green(3),
   black(4),
   null(5)
}

I need a solution to iterate over the listOfCars, get the map of colors and remove the null key from that. Trying to see any other options in Java8 rather than using an Iterator.

Thanks!

Answer 1

Considering a map cannot contain duplicate keys, we can, therefore, say that each Map instance of a Car instance will only ever have at most one entry with a null key.

The solution using the Java-8 forEach construct is:

listOfCars.forEach(e -> e.getColors().remove(null));

Although it can be done with a for loop or an enhanced for loop as well.