I have the following problem:
Goal: Remove from list the animal with "danger" == true;
Restraints: One of the functional interfaces (Consumer, Predicate, Function or Supplier) must be used (I chose BiConsumer because of the index);
Issue: BiConsumer is not updating the passed list (No error is displayed);
Attempts: I have also tried having a list inside removeDangerousAnimal, so that I could then do something like:
static List<Animal> removeDangerousAnimal(List<Animal> listOfAnimals) {
List<Animal> newList = new Arraylist<>();
BiConsumer<Boolean, Integer> removeDangerous = (isDangerous, index) -> {
if(isDangerous == true){
System.out.println("Dangerous animal: " + listOfAnimals.get(index).getName());
listOfAnimals.remove(index);
newList = listOfAnimals;
}
};
But I have learned that with lambdas local variables are immutable (Error: "Variable used in lambda expression should be final or effectively final").
Question: I do not understand why BiConsumer is not updating my list.
Main:
public class Main {
public static void main(String[] args) {
List<Animal> animals = new ArrayList<>();
Dog dog = new Dog("Tom", "He's a good boy", "Chihuahua", 10, 0.30, false, "Dry food", 0.20);
Cat cat = new Cat("Misty", "She has a temper!", "Tigress", 6, 0.40, true, "Soggy food", 0.5);
Bird bird = new Bird("Twitty", "He's very cute!", "Parrot", 1.5, 0.15, false, "Dry food", 0.10);
animals.add(dog);
animals.add(cat);
animals.add(bird);
animals = removeDangerousAnimal(animals);
for (Animal a: animals) {
System.out.println("Animal name: " + a.getName());
}
}
static List<Animal> removeDangerousAnimal(List<Animal> listOfAnimals){
BiConsumer<Boolean, Integer> removeDangerous = (isDangerous, index) -> {
if(isDangerous == true){
System.out.println("Dangerous animal: " + listOfAnimals.get(index).getName());
listOfAnimals.remove(index);
}
};
for (int i = 0; i < listOfAnimals.size(); i++) {
//System.out.println("Animal name: " + a.getName() + " " + a.isDanger());
removeDangerous.accept(listOfAnimals.get(i).isDanger(), i);
}
return listOfAnimals;
}
}
Animal:
public class Animal {
private String name;
private String description;
private String race;
private double weight;
private double height;
private boolean danger;
private String food;
private double foodQuantity;
//---------------------------
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getRace() {
return race;
}
public void setRace(String race) {
this.race = race;
}
public double getWeight() {
return weight;
}
public void setWeight(double weight) {
this.weight = weight;
}
public double getHeight() {
return height;
}
public void setHeight(double height) {
this.height = height;
}
public boolean isDanger() {
return danger;
}
public void setDanger(boolean danger) {
this.danger = danger;
}
public String getFood() {
return food;
}
public void setFood(String food) {
this.food = food;
}
public double getFoodQuantity() {
return foodQuantity;
}
public void setFoodQuantity(double foodQuantity) {
this.foodQuantity = foodQuantity;
}
}
Dog:
public class Dog extends Animal {
private String name;
private String description;
private String race;
private double weight;
private double height;
private boolean danger;
private String food;
private double foodQuantity;
//---------------------------
public Dog(String name, String description, String race, double weight, double height, boolean danger, String food, double foodQuantity) {
this.name = name;
this.description = description;
this.race = race;
this.weight = weight;
this.height = height;
this.danger = danger;
this.food = food;
this.foodQuantity = foodQuantity;
}
public Dog() {
}
//---------------------------
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getRace() {
return race;
}
public void setRace(String race) {
this.race = race;
}
public double getWeight() {
return weight;
}
public void setWeight(double weight) {
this.weight = weight;
}
public double getHeight() {
return height;
}
public void setHeight(double height) {
this.height = height;
}
public boolean isDanger() {
return danger;
}
public void setDanger(boolean danger) {
this.danger = danger;
}
public String getFood() {
return food;
}
public void setFood(String food) {
this.food = food;
}
public double getFoodQuantity() {
return foodQuantity;
}
public void setFoodQuantity(double foodQuantity) {
this.foodQuantity = foodQuantity;
}
}
Cat:
public class Cat extends Animal {
private String name;
private String description;
private String race;
private double weight;
private double height;
private boolean danger;
private String food;
private double foodQuantity;
//---------------------------
public Cat(String name, String description, String race, double weight, double height, boolean danger, String food, double foodQuantity) {
this.name = name;
this.description = description;
this.race = race;
this.weight = weight;
this.height = height;
this.danger = danger;
this.food = food;
this.foodQuantity = foodQuantity;
}
public Cat() {
}
//---------------------------
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getRace() {
return race;
}
public void setRace(String race) {
this.race = race;
}
public double getWeight() {
return weight;
}
public void setWeight(double weight) {
this.weight = weight;
}
public double getHeight() {
return height;
}
public void setHeight(double height) {
this.height = height;
}
public boolean isDanger() {
return danger;
}
public void setDanger(boolean danger) {
this.danger = danger;
}
public String getFood() {
return food;
}
public void setFood(String food) {
this.food = food;
}
public double getFoodQuantity() {
return foodQuantity;
}
public void setFoodQuantity(double foodQuantity) {
this.foodQuantity = foodQuantity;
}
}
Bird:
public class Bird extends Animal {
private String name;
private String description;
private String race;
private double weight;
private double height;
private boolean danger;
private String food;
private double foodQuantity;
//---------------------------
public Bird(String name, String description, String race, double weight, double height, boolean danger, String food, double foodQuantity) {
this.name = name;
this.description = description;
this.race = race;
this.weight = weight;
this.height = height;
this.danger = danger;
this.food = food;
this.foodQuantity = foodQuantity;
}
public Bird() {
}
//---------------------------
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getRace() {
return race;
}
public void setRace(String race) {
this.race = race;
}
public double getWeight() {
return weight;
}
public void setWeight(double weight) {
this.weight = weight;
}
public double getHeight() {
return height;
}
public void setHeight(double height) {
this.height = height;
}
public boolean isDanger() {
return danger;
}
public void setDanger(boolean danger) {
this.danger = danger;
}
public String getFood() {
return food;
}
public void setFood(String food) {
this.food = food;
}
public double getFoodQuantity() {
return foodQuantity;
}
public void setFoodQuantity(double foodQuantity) {
this.foodQuantity = foodQuantity;
}
}
This may be missing the point of the question, but you could use removeIf and pass a Predicate that's based on the isDanger property:
animals.removeIf(Animal::isDanger)