How to get a total value from an ArrayList of enums

August 13, 2022

I’ve have an ArrayList<Herbs> which stores these enums below

public enum Herbs{
    OLD_SPICE(20),
    PURPLE_LOTUS(50);

    private final int points;

    Herbs(int points) {
        this.points = points;
    }

    public int getPoints() {
        return points;
    }
}

and my array list

herbs = new ArrayList<>(Arrays.asList(Herbs.OLD_SPICE, Herbs.PURPLE_LOTUS));

how can I can collects the point values of this enums in this ArrayList? So far I’ve tried to this but really couldn’t make it work.

public int getTotalPoints(ArrayList<Herbs> herbs) {
    ArrayList<Herbs> enumValues = Arrays.asList(herbs.values());
}

This is my second week in Java so don’t judge :))) my goal is to get a total value of points from herbs , something like reduce() method in Javascript.

>Solution :

You can extract the points from each Herbs member by applying mapToInt() which returns IntStream, and then apply sum() to obtain the total.

int totalPoints = herbs.stream()
    .mapToInt(Herbs::getPoints)
    .sum();

Sidenote: usually, names of classes (and is a special form class) are singular. If an instance of a class is meant to represent a single object, a singular noun would be more suitable for its name. For example, Month and DayOfWeek enum-classes from the java.time package.