Avoid combining get and add operations on lists

Medium

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JavaDemetergetter

Modifying a list returned by a getter is a bad pratice.

The returned list might be null, a copy or immutable.

That's why the modification should be encapsulated.

This practice was created by Arolla.

Examples

Example 1:

Negative

Incorrect implementation that violates the practice.

package dev.best.practices;

import java.util.ArrayList;
import java.util.List;

public class Zoo {
    private final List<Animal> animals = new ArrayList<>();

    public static Zoo create() {
        final Zoo zoo = new Zoo();
        zoo.getAnimals().add(new Animal("toto", Species.DOG));
        zoo.getAnimals().add(new Animal("medor", Species.DOG));
        zoo.getAnimals().add(new Animal("kiki", Species.CAT));
        zoo.getAnimals().add(new Animal("nemo", Species.FISH));
        return zoo;
    }

    public List<Animal> getAnimals() {
        return animals;
    }

    public static class Animal {
        private final String name;
        private final Species species;

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

        public boolean hasSpecies(Species species) {
            return this.species == species;
        }
    }

    public enum Species {
        CAT, DOG, FISH, SNAKE, SHEEP, COW, LION, ELEPHANT
    }
}