Avoid combining get and equals on enum

Medium

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JavaDemetergetter

Instead of defining a getter for an enum, add one method per enum value checking if the object matches the value.

Advantages

• readability
• hides the enum type
• hides the enum values
• can be used as a predicate

Examples

Example 1:

Positive

Correct implementation following the practice.

package dev.best.practices;

import java.util.List;

public class Zoo {
    private final List<Animal> animals;

    public Zoo(List<Animal> animals) {
        this.animals = animals;
    }

    public long dogsCount() {
        return animals.stream()
                .filter(Animal::isDog)
                .count();
    }

    public static class Animal {
        private final Species species;

        public Animal(Species species) {
            this.species = species;
        }

        public boolean isDog() {
            return species == Species.DOG;
        }
    }

    public enum Species {
        CAT, DOG
    }
}

Negative

Incorrect implementation that violates the practice.

package dev.best.practices;

import java.util.List;

public class Zoo {
    private final List<Animal> animals;

    public Zoo(List<Animal> animals) {
        this.animals = animals;
    }

    public long dogsCount() {
        return animals.stream()
                .filter(animal -> animal.getSpecies() == Species.DOG)
                .count();
    }

    public static class Animal {
        private final Species species;

        public Animal(Species species) {
            this.species = species;
        }

        public Species getSpecies() {
            return species;
        }
    }

    public enum Species {
        CAT, DOG
    }
}