(→Conceito de Rato: Mouse) |
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Considere que a energia disponível inicialmente para os cães, gatos, pássaros e ratos é, respectivamente, de 1000, 500, 20 e 50 unidades. Quando os animais correm, gastam, respectivamente, 50, 25, 5 e 2 unidades. Um pássaro, quando voa, gasta apenas 2 unidades. Um cão que ataque um gato gasta 100 unidades e faz com que o gato perca 25. | Considere que a energia disponível inicialmente para os cães, gatos, pássaros e ratos é, respectivamente, de 1000, 500, 20 e 50 unidades. Quando os animais correm, gastam, respectivamente, 50, 25, 5 e 2 unidades. Um pássaro, quando voa, gasta apenas 2 unidades. Um cão que ataque um gato gasta 100 unidades e faz com que o gato perca 25. | ||
− | Para um predador comer uma presa tem de a perseguir para a capturar (podendo a perseguição ser ou não bem sucedida). Um cão consegue capturar um rato em cada 25 tentativas. Para os gatos, o rácio é 1 em 5 (ratos) e 1 em 10 (pássaros). A perseguição consome a mesma energia que correr (para cada interveniente), mas a presa recebe um bónus de 5 unidades se escapar. Se a presa estiver a dormir, é apanhada 1 em cada 2 tentativas. | + | Para um predador comer uma presa tem de a perseguir para a capturar (podendo a perseguição ser ou não bem sucedida). Um cão consegue capturar um rato em cada 25 tentativas. Para os gatos, o rácio é 1 em 5 (ratos) e 1 em 10 (pássaros). A perseguição consome a mesma energia que correr (para cada interveniente), mas a presa recebe um bónus de 5 unidades se escapar. <!--Se a presa estiver a dormir, é apanhada 1 em cada 2 tentativas.--> |
Construa uma aplicação onde existem 2 cães ("Piloto" e "Átila"), 3 gatos ("Tareco", "Pantufa" e "Kitty"), 20 pássaros e 50 ratos (os pássaros e ratos podem ser organizados em arrays). | Construa uma aplicação onde existem 2 cães ("Piloto" e "Átila"), 3 gatos ("Tareco", "Pantufa" e "Kitty"), 20 pássaros e 50 ratos (os pássaros e ratos podem ser organizados em arrays). | ||
Line 47: | Line 47: | ||
{{CollapsedCode|Ficheiro '''Dog.java'''| | {{CollapsedCode|Ficheiro '''Dog.java'''| | ||
− | < | + | <source lang="java"> |
public class Dog { | public class Dog { | ||
− | + | /** | |
− | + | * We define the base energy as a constant, but it does not have to be this | |
− | + | * way. It could be defined differently for each dog (but this requirement | |
− | + | * does not exist in this case). | |
− | + | */ | |
− | + | private static final int BASE_ENERGY = 1000; | |
− | + | /** | |
− | + | * The dog's name. | |
− | + | */ | |
− | + | private String _name; | |
− | + | /** | |
− | + | * The dog's current energy value. | |
− | + | */ | |
− | + | private int _energy = BASE_ENERGY; | |
− | + | /** | |
− | + | * Initialize a dog with a name. Default energy levels are used. | |
− | + | * | |
− | + | * @param name | |
− | + | */ | |
− | + | public Dog(String name) { | |
− | + | _name = name; | |
− | + | } | |
− | + | /** | |
− | + | * @return dog's current energy level. | |
− | + | */ | |
− | + | public int getEnergy() { | |
− | + | return _energy; | |
− | + | } | |
− | + | /** | |
− | + | * @return dog's name | |
− | + | */ | |
− | + | public String getName() { | |
− | + | return _name; | |
− | + | } | |
− | + | /** | |
− | + | * Set the dog's name | |
− | + | * | |
− | + | * @param name | |
− | + | * the dog's name | |
− | + | */ | |
− | + | public void setName(String name) { | |
− | + | _name = name; | |
− | + | } | |
− | + | /** | |
− | + | * When a dog runs, the energy decreases by 50 units. This value could be | |
− | + | * defined as an attribute or as a constant. | |
− | + | * | |
− | + | * @return whether the dog was able to run. | |
− | + | */ | |
− | + | public boolean run() { | |
− | + | if (_energy < 50) | |
− | + | return false; | |
− | + | _energy -= 50; | |
− | + | return true; | |
− | + | } | |
− | + | /** | |
− | + | * Call "run" to account for spent energy. | |
− | + | * | |
− | + | * @param mouse | |
− | + | * the mouse to be chased. | |
− | + | * @return whether the dog was able to catch the mouse. If the mouse | |
− | + | * escapes, its energy increases. | |
− | + | */ | |
− | + | public boolean caughtMouse(Mouse mouse) { | |
− | + | run(); | |
− | + | mouse.run(); | |
− | + | if (0 == (int) (25 * Math.random())) { | |
− | + | return true; | |
− | + | } | |
− | + | mouse.escaped(); | |
− | + | return false; | |
− | + | } | |
− | + | /** | |
− | + | * Eating is more or less like a vampire feeding... | |
− | + | * | |
− | + | * @param mouse | |
− | + | * the mouse to eat. | |
− | + | */ | |
− | + | public void eatMouse(Mouse mouse) { | |
− | + | if (caughtMouse(mouse)) | |
− | + | _energy += mouse.drain(); | |
− | + | } | |
− | + | /** | |
− | + | * We assume that the dog is always able to attack the cat. The parameter to | |
− | + | * ''attacked'' is used to specify the amount of energy lost by the cat. | |
− | + | * Note that we are assuming that the degree of loss depends on the attacker | |
− | + | * (hence the value being defined in the dog class). | |
− | + | * | |
− | + | * The energy values could be defined as attributes or as constants. | |
− | + | * | |
− | + | * @param cat | |
− | + | * the cat the dog attacks | |
− | + | */ | |
− | + | public void attackCat(Cat cat) { | |
− | + | _energy -= 100; | |
− | + | cat.attacked(25); | |
− | + | } | |
− | + | /** | |
− | + | * Energy is recovered when sleeping. | |
− | + | */ | |
− | + | public void sleep() { | |
− | + | _energy = BASE_ENERGY; | |
− | + | } | |
− | + | /** | |
− | + | * @see java.lang.Object#equals(java.lang.Object) | |
− | + | */ | |
− | + | @Override | |
− | + | public boolean equals(Object o) { | |
− | + | if (o instanceof Dog) { | |
− | + | Dog dog = (Dog) o; | |
− | + | return _name.equals(dog.getName()) && _energy == dog.getEnergy(); | |
− | + | } | |
− | + | return false; | |
− | + | } | |
− | + | /** | |
− | + | * @see java.lang.Object#toString() | |
− | + | */ | |
− | + | @Override | |
− | + | public String toString() { | |
− | + | return _name + " (dog) (" + _energy + ")"; | |
− | + | } | |
− | |||
} | } | ||
− | </ | + | </source> |
}} | }} | ||
Line 192: | Line 191: | ||
{{CollapsedCode|Ficheiro '''Cat.java'''| | {{CollapsedCode|Ficheiro '''Cat.java'''| | ||
− | < | + | <source lang="java"> |
public class Cat { | public class Cat { | ||
− | + | /** | |
− | + | * We define the base energy as a constant, but it does not have to be this | |
− | + | * way. It could be defined differently for each dog (but this requirement | |
− | + | * does not exist in this case). | |
− | + | */ | |
− | + | private static final int BASE_ENERGY = 500; | |
− | + | /** | |
− | + | * The cat's name. | |
− | + | */ | |
− | + | private String _name; | |
− | + | /** | |
− | + | * The cat's current energy value. | |
− | + | */ | |
− | + | private int _energy = BASE_ENERGY; | |
− | + | /** | |
− | + | * Initialize a cat with a name. Default energy levels are used. | |
− | + | * | |
− | + | * @param name | |
− | + | */ | |
− | + | public Cat(String name) { | |
− | + | _name = name; | |
− | + | } | |
− | + | /** | |
− | + | * @return cat's current energy level. | |
− | + | */ | |
− | + | public int getEnergy() { | |
− | + | return _energy; | |
− | + | } | |
− | + | /** | |
− | + | * @return cat's name | |
− | + | */ | |
− | + | public String getName() { | |
− | + | return _name; | |
− | + | } | |
− | + | /** | |
− | + | * Set the cat's name | |
− | + | * | |
− | + | * @param name | |
− | + | * the cat's name | |
− | + | */ | |
− | + | public void setName(String name) { | |
− | + | _name = name; | |
− | + | } | |
− | + | /** | |
− | + | * When a cat runs, the energy decreases by 25 units. This value could be | |
− | + | * defined as an attribute or as a constant. | |
− | + | * | |
− | + | * @return whether the cat was able to run. | |
− | + | */ | |
− | + | public boolean run() { | |
− | + | if (_energy < 25) | |
− | + | return false; | |
− | + | _energy -= 25; | |
− | + | return true; | |
− | + | } | |
− | + | /** | |
− | + | * Call "run" to account for spent energy. | |
− | + | * | |
− | + | * @param mouse | |
− | + | * the mouse to be caught. | |
− | + | * @return whether the cat was able to catch the mouse. If the mouse | |
− | + | * escapes, its energy increases. | |
− | + | */ | |
− | + | public boolean caughtMouse(Mouse mouse) { | |
− | + | run(); | |
− | + | mouse.run(); | |
− | + | if (0 == (int) (5 * Math.random())) { | |
− | + | return true; | |
− | + | } | |
− | + | mouse.escaped(); | |
− | + | return false; | |
− | + | } | |
− | + | /** | |
− | + | * Call "run" ("fly"??) to account for spent energy. | |
− | + | * | |
− | + | * @param bird | |
− | + | * the bird to be caught. | |
− | + | * @return whether the cat was able to catch the bird. If the bird escapes, | |
− | + | * its energy increases. | |
− | + | */ | |
− | + | public boolean caughtBird(Bird bird) { | |
− | + | run(); | |
− | + | bird.fly(); // run?? | |
− | + | if (0 == (int) (10 * Math.random())) { | |
− | + | return true; | |
− | + | } | |
− | + | bird.escaped(); | |
− | + | return false; | |
− | + | } | |
− | + | /** | |
− | + | * Eating is more or less like a vampire feeding... | |
− | + | * | |
− | + | * @param mouse | |
− | + | * the mouse to eat. | |
− | + | */ | |
− | + | public void eatMouse(Mouse mouse) { | |
− | + | if (caughtMouse(mouse)) | |
− | + | _energy += mouse.drain(); | |
− | + | } | |
− | + | /** | |
− | + | * Eating is more or less like a vampire feeding... | |
− | + | * | |
− | + | * @param bird | |
− | + | * the mouse to eat. | |
− | + | */ | |
− | + | public void eatBird(Bird bird) { | |
− | + | if (caughtBird(bird)) | |
− | + | _energy += bird.drain(); | |
− | + | } | |
− | + | /** | |
− | + | * We should probably check for large decrease values. Nevertheless, in this | |
− | + | * case, for simplicity, we will let the energy go negative and, later on, | |
− | + | * the cat can recover after a nap. | |
− | + | * | |
− | + | * @param energyDecrease | |
− | + | */ | |
− | + | public void attacked(int energyDecrease) { | |
− | + | _energy -= energyDecrease; | |
− | + | } | |
− | + | /** | |
− | + | * Energy is recovered when sleeping. | |
− | + | */ | |
− | + | public void sleep() { | |
− | + | _energy = BASE_ENERGY; | |
− | + | } | |
− | + | /** | |
− | + | * @see java.lang.Object#equals(java.lang.Object) | |
− | + | */ | |
− | + | @Override | |
− | + | public boolean equals(Object o) { | |
− | + | if (o instanceof Cat) { | |
− | + | Cat cat = (Cat) o; | |
− | + | return _name.equals(cat.getName()) && _energy == cat.getEnergy(); | |
− | + | } | |
− | + | return false; | |
− | + | } | |
− | + | /** | |
− | + | * @see java.lang.Object#toString() | |
− | + | */ | |
− | + | @Override | |
− | + | public String toString() { | |
− | + | return _name + " (cat) (" + _energy + ")"; | |
− | + | } | |
− | |||
} | } | ||
− | </ | + | </source> |
}} | }} | ||
Line 361: | Line 359: | ||
{{CollapsedCode|Ficheiro '''Mouse.java'''| | {{CollapsedCode|Ficheiro '''Mouse.java'''| | ||
− | < | + | <source lang="java"> |
public class Mouse { | public class Mouse { | ||
Line 386: | Line 384: | ||
* When a mouse runs, the energy decreases by 2 units. This value could be | * When a mouse runs, the energy decreases by 2 units. This value could be | ||
* defined as an attribute or as a constant. | * defined as an attribute or as a constant. | ||
− | * | + | * |
* @return whether the mouse was able to run. | * @return whether the mouse was able to run. | ||
*/ | */ | ||
Line 439: | Line 437: | ||
} | } | ||
} | } | ||
− | </ | + | </source> |
}} | }} | ||
− | == Conceito de Pássaro | + | == Conceito de Pássaro == |
− | < | + | {{CollapsedCode|Ficheiro '''Bird.java'''| |
+ | <source lang="java"> | ||
public class Bird { | public class Bird { | ||
Line 469: | Line 468: | ||
* When a bird runs, the energy decreases by 5 units. This value could be | * When a bird runs, the energy decreases by 5 units. This value could be | ||
* defined as an attribute or as a constant. | * defined as an attribute or as a constant. | ||
− | * | + | * |
* @return whether the bird was able to run. | * @return whether the bird was able to run. | ||
*/ | */ | ||
Line 482: | Line 481: | ||
* When a bird flies, the energy decreases by 2 units. This value could be | * When a bird flies, the energy decreases by 2 units. This value could be | ||
* defined as an attribute or as a constant. | * defined as an attribute or as a constant. | ||
− | * | + | * |
* @return whether the bird was able to fly. | * @return whether the bird was able to fly. | ||
*/ | */ | ||
Line 535: | Line 534: | ||
} | } | ||
} | } | ||
− | </ | + | </source> |
+ | }} | ||
== Programa Principal == | == Programa Principal == | ||
Este programa implementa o cenário descrito no enunciado do problema. | Este programa implementa o cenário descrito no enunciado do problema. | ||
− | < | + | |
− | + | {{CollapsedCode|Ficheiro '''Application.java'''| | |
+ | <source lang="java"> | ||
public class Application { | public class Application { | ||
− | + | /** | |
− | + | * @param args | |
− | + | */ | |
− | + | public static void main(String[] args) { | |
− | + | Dog d1 = new Dog("Piloto"); | |
− | + | Dog d2 = new Dog("Átila"); | |
− | + | Cat c1 = new Cat("Tareco"); | |
− | + | Cat c2 = new Cat("Pantufa"); | |
− | + | Cat c3 = new Cat("Kitty"); | |
− | + | ||
− | + | Bird[] birds = new Bird[20]; | |
− | + | for (int ix = 0; ix < birds.length; ix++) | |
− | + | birds[ix] = new Bird(); | |
− | + | Mouse[] mice = new Mouse[50]; | |
− | + | for (int ix = 0; ix < mice.length; ix++) | |
− | + | mice[ix] = new Mouse(); | |
− | + | // snapshot: present everything | |
− | + | System.out.println("BEFORE"); | |
− | + | System.out.println(d1); | |
− | + | System.out.println(d2); | |
− | + | System.out.println(c1); | |
− | + | System.out.println(c2); | |
− | + | System.out.println(c3); | |
− | + | for (int ix = 0; ix < birds.length; ix++) | |
− | + | System.out.println(birds[ix]); | |
− | + | for (int ix = 0; ix < mice.length; ix++) | |
− | + | System.out.println(mice[ix]); | |
− | + | // run, chase, eat, sleep, etc. | |
− | + | for (int ix = 0; ix < birds.length; ix++) | |
− | + | birds[ix].fly(); | |
− | + | d1.run(); | |
− | + | d2.attackCat(c1); | |
− | + | c2.eatBird(birds[2]); | |
− | + | c3.eatBird(birds[9]); | |
− | + | c3.eatMouse(mice[0]); | |
− | + | d2.eatMouse(mice[1]); | |
− | + | mice[3].run(); | |
− | + | // snapshot: present everything | |
− | + | System.out.println("AFTER"); | |
− | + | System.out.println(d1); | |
− | + | System.out.println(d2); | |
− | + | System.out.println(c1); | |
− | + | System.out.println(c2); | |
− | + | System.out.println(c3); | |
− | + | for (int ix = 0; ix < birds.length; ix++) | |
− | + | System.out.println(birds[ix]); | |
− | + | for (int ix = 0; ix < mice.length; ix++) | |
− | + | System.out.println(mice[ix]); | |
− | + | } | |
} | } | ||
− | </ | + | </source> |
+ | }} | ||
= Compilação e Execução = | = Compilação e Execução = |
Numa casa de campo existem vários animais.
Alguns animais são domésticos: cães, gatos e pássaros (canários, etc.). Os donos acreditam em dar liberdade completa aos animais, o que causa alguns problemas de interacção nem sempre do agrado geral.
Outros animais, embora vivam na casa ou perto dela, não são oficialmente considerados animais domésticos: ratos, cobras, insectos, aranhas, etc. Estes animais também se deslocam pela propriedade, livre mas nem sempre impunemente.
Todos os animais podem correr (e os pássaros voar), consumindo energia para o efeito. Quando a energia termina, não podem correr mais e têm de dormir para recuperar forças.
Além do repouso, os cães e os gatos podem recuperar energia comendo ratos. Um rato devorado perde, claro está, toda a energia (é transferida para o predador). Os gatos, por serem ágeis, também conseguem comer pássaros (com efeitos muito semelhantes aos da relação gato-rato).
Por vezes, os cães perdem a paciência e atacam os gatos. Ambos perdem energia no processo.
Modele os conceitos "cão", "gato", "pássaro" e "rato". Além da energia, os cães e os gatos têm nome (uma cadeia de caracteres).
Considere que a energia disponível inicialmente para os cães, gatos, pássaros e ratos é, respectivamente, de 1000, 500, 20 e 50 unidades. Quando os animais correm, gastam, respectivamente, 50, 25, 5 e 2 unidades. Um pássaro, quando voa, gasta apenas 2 unidades. Um cão que ataque um gato gasta 100 unidades e faz com que o gato perca 25.
Para um predador comer uma presa tem de a perseguir para a capturar (podendo a perseguição ser ou não bem sucedida). Um cão consegue capturar um rato em cada 25 tentativas. Para os gatos, o rácio é 1 em 5 (ratos) e 1 em 10 (pássaros). A perseguição consome a mesma energia que correr (para cada interveniente), mas a presa recebe um bónus de 5 unidades se escapar.
Construa uma aplicação onde existem 2 cães ("Piloto" e "Átila"), 3 gatos ("Tareco", "Pantufa" e "Kitty"), 20 pássaros e 50 ratos (os pássaros e ratos podem ser organizados em arrays).
Neste cenário, os gatos correm, perseguem pássaros e ratos e são atacados pelos cães, que também podem correr e perseguir e comer ratos. Os animais dormem automaticamente se ficam sem energia (excepto quando são devorados: nesse caso devem ser considerados mortos).
Apresente o estado inicial dos animais (métodos toString) e o estado final (depois de algumas interacções).
(Pode utilizar parte do resultado do Exercício 01 na resolução deste exercicio.)
A solução apresentada procura manter-se simples e a um nível que ainda não implica utilizar abstracção de propriedade comuns, como por exemplo, a energia, ou de conceitos mais básicos (o de Animal, por exemplo). Estes aspectos, necessários numa boa definição de solução, são objecto de estudo em fases mais adiantadas da exposição da matéria.
Neste caso, como se escolheu (dada a fase introdutória) não representar os conceitos hierarquizados, apenas existem relações de dependência entre as classes (representadas pelas setas a tracejado).
Existem opções de desenho sub-óptimas. Consegue detectá-las?
BUG: o método "escaped" deveria ter como tipo de retorno "void" e não "boolean".
Diagrama de classes |
---|
Ficheiro Dog.java |
---|
public class Dog {
/**
* We define the base energy as a constant, but it does not have to be this
* way. It could be defined differently for each dog (but this requirement
* does not exist in this case).
*/
private static final int BASE_ENERGY = 1000;
/**
* The dog's name.
*/
private String _name;
/**
* The dog's current energy value.
*/
private int _energy = BASE_ENERGY;
/**
* Initialize a dog with a name. Default energy levels are used.
*
* @param name
*/
public Dog(String name) {
_name = name;
}
/**
* @return dog's current energy level.
*/
public int getEnergy() {
return _energy;
}
/**
* @return dog's name
*/
public String getName() {
return _name;
}
/**
* Set the dog's name
*
* @param name
* the dog's name
*/
public void setName(String name) {
_name = name;
}
/**
* When a dog runs, the energy decreases by 50 units. This value could be
* defined as an attribute or as a constant.
*
* @return whether the dog was able to run.
*/
public boolean run() {
if (_energy < 50)
return false;
_energy -= 50;
return true;
}
/**
* Call "run" to account for spent energy.
*
* @param mouse
* the mouse to be chased.
* @return whether the dog was able to catch the mouse. If the mouse
* escapes, its energy increases.
*/
public boolean caughtMouse(Mouse mouse) {
run();
mouse.run();
if (0 == (int) (25 * Math.random())) {
return true;
}
mouse.escaped();
return false;
}
/**
* Eating is more or less like a vampire feeding...
*
* @param mouse
* the mouse to eat.
*/
public void eatMouse(Mouse mouse) {
if (caughtMouse(mouse))
_energy += mouse.drain();
}
/**
* We assume that the dog is always able to attack the cat. The parameter to
* ''attacked'' is used to specify the amount of energy lost by the cat.
* Note that we are assuming that the degree of loss depends on the attacker
* (hence the value being defined in the dog class).
*
* The energy values could be defined as attributes or as constants.
*
* @param cat
* the cat the dog attacks
*/
public void attackCat(Cat cat) {
_energy -= 100;
cat.attacked(25);
}
/**
* Energy is recovered when sleeping.
*/
public void sleep() {
_energy = BASE_ENERGY;
}
/**
* @see java.lang.Object#equals(java.lang.Object)
*/
@Override
public boolean equals(Object o) {
if (o instanceof Dog) {
Dog dog = (Dog) o;
return _name.equals(dog.getName()) && _energy == dog.getEnergy();
}
return false;
}
/**
* @see java.lang.Object#toString()
*/
@Override
public String toString() {
return _name + " (dog) (" + _energy + ")";
}
}
|
Ficheiro Cat.java |
---|
public class Cat {
/**
* We define the base energy as a constant, but it does not have to be this
* way. It could be defined differently for each dog (but this requirement
* does not exist in this case).
*/
private static final int BASE_ENERGY = 500;
/**
* The cat's name.
*/
private String _name;
/**
* The cat's current energy value.
*/
private int _energy = BASE_ENERGY;
/**
* Initialize a cat with a name. Default energy levels are used.
*
* @param name
*/
public Cat(String name) {
_name = name;
}
/**
* @return cat's current energy level.
*/
public int getEnergy() {
return _energy;
}
/**
* @return cat's name
*/
public String getName() {
return _name;
}
/**
* Set the cat's name
*
* @param name
* the cat's name
*/
public void setName(String name) {
_name = name;
}
/**
* When a cat runs, the energy decreases by 25 units. This value could be
* defined as an attribute or as a constant.
*
* @return whether the cat was able to run.
*/
public boolean run() {
if (_energy < 25)
return false;
_energy -= 25;
return true;
}
/**
* Call "run" to account for spent energy.
*
* @param mouse
* the mouse to be caught.
* @return whether the cat was able to catch the mouse. If the mouse
* escapes, its energy increases.
*/
public boolean caughtMouse(Mouse mouse) {
run();
mouse.run();
if (0 == (int) (5 * Math.random())) {
return true;
}
mouse.escaped();
return false;
}
/**
* Call "run" ("fly"??) to account for spent energy.
*
* @param bird
* the bird to be caught.
* @return whether the cat was able to catch the bird. If the bird escapes,
* its energy increases.
*/
public boolean caughtBird(Bird bird) {
run();
bird.fly(); // run??
if (0 == (int) (10 * Math.random())) {
return true;
}
bird.escaped();
return false;
}
/**
* Eating is more or less like a vampire feeding...
*
* @param mouse
* the mouse to eat.
*/
public void eatMouse(Mouse mouse) {
if (caughtMouse(mouse))
_energy += mouse.drain();
}
/**
* Eating is more or less like a vampire feeding...
*
* @param bird
* the mouse to eat.
*/
public void eatBird(Bird bird) {
if (caughtBird(bird))
_energy += bird.drain();
}
/**
* We should probably check for large decrease values. Nevertheless, in this
* case, for simplicity, we will let the energy go negative and, later on,
* the cat can recover after a nap.
*
* @param energyDecrease
*/
public void attacked(int energyDecrease) {
_energy -= energyDecrease;
}
/**
* Energy is recovered when sleeping.
*/
public void sleep() {
_energy = BASE_ENERGY;
}
/**
* @see java.lang.Object#equals(java.lang.Object)
*/
@Override
public boolean equals(Object o) {
if (o instanceof Cat) {
Cat cat = (Cat) o;
return _name.equals(cat.getName()) && _energy == cat.getEnergy();
}
return false;
}
/**
* @see java.lang.Object#toString()
*/
@Override
public String toString() {
return _name + " (cat) (" + _energy + ")";
}
}
|
Ficheiro Mouse.java |
---|
public class Mouse {
/**
* We define the base energy as a constant, but it does not have to be this
* way. It could be defined differently for each dog (but this requirement
* does not exist in this case).
*/
private static final int BASE_ENERGY = 50;
/**
* The mouse's current energy value.
*/
private int _energy = BASE_ENERGY;
/**
* @return mouse's current energy level.
*/
public int getEnergy() {
return _energy;
}
/**
* When a mouse runs, the energy decreases by 2 units. This value could be
* defined as an attribute or as a constant.
*
* @return whether the mouse was able to run.
*/
public boolean run() {
if (_energy < 2)
return false;
_energy -= 2;
return true;
}
/**
* Energy goes up 5 points in a narrow escape.
*/
public void escaped() {
_energy += 5;
}
/**
* @return the energy level in this mouse
*/
public int drain() {
int energy = _energy;
_energy = 0;
return energy;
}
/**
* Energy is recovered when sleeping.
*/
public void sleep() {
_energy = BASE_ENERGY;
}
/**
* @see java.lang.Object#equals(java.lang.Object)
*/
@Override
public boolean equals(Object o) {
if (o instanceof Mouse) {
Mouse mouse = (Mouse) o;
return _energy == mouse.getEnergy();
}
return false;
}
/**
* @see java.lang.Object#toString()
*/
@Override
public String toString() {
return "mouse (" + _energy + ")";
}
}
|
Ficheiro Bird.java |
---|
public class Bird {
/**
* We define the base energy as a constant, but it does not have to be this
* way. It could be defined differently for each dog (but this requirement
* does not exist in this case).
*/
private static final int BASE_ENERGY = 20;
/**
* The bird's current energy value.
*/
private int _energy = BASE_ENERGY;
/**
* @return mouse's current energy level.
*/
public int getEnergy() {
return _energy;
}
/**
* When a bird runs, the energy decreases by 5 units. This value could be
* defined as an attribute or as a constant.
*
* @return whether the bird was able to run.
*/
public boolean run() {
if (_energy < 5)
return false;
_energy -= 5;
return true;
}
/**
* When a bird flies, the energy decreases by 2 units. This value could be
* defined as an attribute or as a constant.
*
* @return whether the bird was able to fly.
*/
public boolean fly() {
if (_energy < 2)
return false;
_energy -= 2;
return true;
}
/**
* Energy goes up 5 points in a narrow escape.
*/
public void escaped() {
_energy += 5;
}
/**
* @return the energy level in this mouse
*/
public int drain() {
int energy = _energy;
_energy = 0;
return energy;
}
/**
* Energy is recovered when sleeping.
*/
public void sleep() {
_energy = BASE_ENERGY;
}
/**
* @see java.lang.Object#equals(java.lang.Object)
*/
@Override
public boolean equals(Object o) {
if (o instanceof Bird) {
Bird bird = (Bird) o;
return _energy == bird.getEnergy();
}
return false;
}
/**
* @see java.lang.Object#toString()
*/
@Override
public String toString() {
return "bird (" + _energy + ")";
}
}
|
Este programa implementa o cenário descrito no enunciado do problema.
Ficheiro Application.java |
---|
public class Application {
/**
* @param args
*/
public static void main(String[] args) {
Dog d1 = new Dog("Piloto");
Dog d2 = new Dog("Átila");
Cat c1 = new Cat("Tareco");
Cat c2 = new Cat("Pantufa");
Cat c3 = new Cat("Kitty");
Bird[] birds = new Bird[20];
for (int ix = 0; ix < birds.length; ix++)
birds[ix] = new Bird();
Mouse[] mice = new Mouse[50];
for (int ix = 0; ix < mice.length; ix++)
mice[ix] = new Mouse();
// snapshot: present everything
System.out.println("BEFORE");
System.out.println(d1);
System.out.println(d2);
System.out.println(c1);
System.out.println(c2);
System.out.println(c3);
for (int ix = 0; ix < birds.length; ix++)
System.out.println(birds[ix]);
for (int ix = 0; ix < mice.length; ix++)
System.out.println(mice[ix]);
// run, chase, eat, sleep, etc.
for (int ix = 0; ix < birds.length; ix++)
birds[ix].fly();
d1.run();
d2.attackCat(c1);
c2.eatBird(birds[2]);
c3.eatBird(birds[9]);
c3.eatMouse(mice[0]);
d2.eatMouse(mice[1]);
mice[3].run();
// snapshot: present everything
System.out.println("AFTER");
System.out.println(d1);
System.out.println(d2);
System.out.println(c1);
System.out.println(c2);
System.out.println(c3);
for (int ix = 0; ix < birds.length; ix++)
System.out.println(birds[ix]);
for (int ix = 0; ix < mice.length; ix++)
System.out.println(mice[ix]);
}
}
|
A compilação processa-se como indicado (poder-se-ia compilar ficheiro a ficheiro):
javac Dog.java Cat.java Mouse.java Bird.java javac Application.java
De facto, a compilação do ficheiro Application.java seria suficiente para causar a compilação de todos os outros, já que são referidos a partir dele (o compilador de Java é capaz de seguir dependências explícitas entre classes).
O programa começa a sua execução na função main da classe escolhida para iniciar a aplicação (neste caso, Application):
java Application