124 lines
3.6 KiB
Java
Executable File
124 lines
3.6 KiB
Java
Executable File
import java.util.List;
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import java.util.Random;
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/**
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* A simple model of a rabbit.
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* Rabbits age, move, breed, and die.
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*
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* @author David J. Barnes and Michael Kölling
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* @version 2016.03.18
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*/
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public class Rabbit extends Animal
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{
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// Characteristics shared by all rabbits (class variables).
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// The age at which a rabbit can start to breed.
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private static final int BREEDING_AGE = 5;
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// The age to which a rabbit can live.
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private static final int MAX_AGE = 40;
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// The likelihood of a rabbit breeding.
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private static final double BREEDING_PROBABILITY = 0.12;
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// The maximum number of births.
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private static final int MAX_LITTER_SIZE = 4;
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// A shared random number generator to control breeding.
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private static final Random rand = Randomizer.getRandom();
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// Individual characteristics (instance fields).
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// The rabbit's age.
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private int age;
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/**
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* Create a new rabbit. A rabbit may be created with age
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* zero (a new born) or with a random age.
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*
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* @param randomAge If true, the rabbit will have a random age.
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* @param field The field currently occupied.
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* @param location The location within the field.
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*/
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public Rabbit(boolean randomAge, Field field, Location location)
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{
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super(field, location);
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age = 0;
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if(randomAge) {
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age = rand.nextInt(MAX_AGE);
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}
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}
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/**
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* This is what the rabbit does most of the time - it runs
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* around. Sometimes it will breed or die of old age.
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* @param newRabbits A list to return newly born rabbits.
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*/
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public void act(List<Animal> newRabbits)
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{
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incrementAge();
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if(isAlive()) {
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giveBirth(newRabbits);
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// Try to move into a free location.
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Location newLocation = getField().freeAdjacentLocation(getLocation());
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if(newLocation != null) {
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setLocation(newLocation);
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}
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else {
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// Overcrowding.
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setDead();
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}
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}
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}
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/**
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* Increase the age.
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* This could result in the rabbit's death.
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*/
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private void incrementAge()
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{
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age++;
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if(age > MAX_AGE) {
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setDead();
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}
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}
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/**
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* Check whether or not this rabbit is to give birth at this step.
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* New births will be made into free adjacent locations.
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* @param newRabbits A list to return newly born rabbits.
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*/
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private void giveBirth(List<Animal> newRabbits)
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{
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// New rabbits are born into adjacent locations.
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// Get a list of adjacent free locations.
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Field field = getField();
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List<Location> free = field.getFreeAdjacentLocations(getLocation());
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int births = breed();
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for(int b = 0; b < births && free.size() > 0; b++) {
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Location loc = free.remove(0);
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Rabbit young = new Rabbit(false, field, loc);
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newRabbits.add(young);
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}
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}
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/**
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* Generate a number representing the number of births,
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* if it can breed.
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* @return The number of births (may be zero).
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*/
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private int breed()
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{
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int births = 0;
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if(canBreed() && rand.nextDouble() <= BREEDING_PROBABILITY) {
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births = rand.nextInt(MAX_LITTER_SIZE) + 1;
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}
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return births;
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}
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/**
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* A rabbit can breed if it has reached the breeding age.
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* @return true if the rabbit can breed, false otherwise.
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*/
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private boolean canBreed()
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{
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return age >= BREEDING_AGE;
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}
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}
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