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lab5

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黑墨水鱼
2022-03-19 17:47:52 +08:00
parent 6bf672bd5b
commit 1c8f95c4b3
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66
lab/lab5/Question5/Animal.java Normal file
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/*
* Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
* Date: 2022/03/19
* Description: This is the class of Animal.
*/
public class Animal {
/**
* Animal's name
*/
private String name;
/**
* Animal's weight
*/
private double weight;
/**
* Constructor. Initialize the name and weight of the animal.
*/
public Animal(String name, double weight) {
this.name = name;
this.weight = weight;
}
/**
* Get the name of the animal.
*
* @return the name of the animal
*/
public String getName() {
return name;
}
/**
* Get the weight of the animal.
*
* @return the weight of the animal
*/
public double getWeight() {
return weight;
}
/**
* Set the weight of the animal.
*
* @param weight
* the weight of the animal
*/
public void setWeight(double weight) {
this.weight = weight;
}
/**
* Test
*/
public static void testAnimal() {
Animal animal = new Animal("cat", 1.0);
System.out.println(animal.getName() == "cat");
System.out.println(animal.getWeight() == 1.0);
animal.setWeight(2.0);
System.out.println(animal.getName() == "cat");
System.out.println(animal.getWeight() == 2.0);
}
}

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lab/lab5/Question5/Bird.java Normal file
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/*
* Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
* Date: 2022-03-19
* Description: This is the class of Bird.
*/
public class Bird extends Animal {
/**
* Altitude of the bird.
*/
private double altitude;
/**
* Constructor of Bird.
*
* @param name name of the bird
* @param weight weight of the bird
* @param altitude altitude of the bird
*/
public Bird(String name, double weight, double altitude) {
super(name, weight);
this.altitude = altitude;
}
/**
* Get the altitude of the bird.
*
* @return altitude of the bird
*/
public double getAltitude() {
return altitude;
}
/**
* Test
*/
public static void testBird() {
Bird bird = new Bird("Bird", 1.0, 10.0);
System.out.println(bird.getName() == "Bird");
System.out.println(bird.getWeight() == 1.0);
System.out.println(bird.getAltitude() == 10.0);
}
}

35
lab/lab5/Question5/Cat.java Normal file
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/*
* Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
* Date: 2022-03-19
* Description: Cat class
*/
public class Cat extends Animal {
/**
* Constructor. Initialize the name and weight of the cat
*/
public Cat(String name, double weight) {
super(name, weight);
}
/**
* Feeding a cat adds 1.0 to its weight
*/
public void feed() {
setWeight(getWeight() + 1.0);
}
/**
* Test
*/
public static void testCat() {
Cat c = new Cat("Meow", 2.0);
System.out.println(c.getName() == "Meow");
System.out.println(c.getWeight() == 2.0);
c.feed();
// The name is still the same but the weight increased by 1.0:
System.out.println(c.getName() == "Meow");
System.out.println(c.getWeight() == 3.0);
}
}

34
lab/lab5/Question5/Dog.java Normal file
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/*
* Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
* Date: 2022-03-19
* Description: Dog class
*/
public class Dog extends Animal {
/**
* Constructor. Initialize the name and weight of the dog
*/
public Dog(String name, double weight) {
super(name, weight);
}
/**
* Feeding a dog adds 2.0 to its weight
*/
public void feed() {
setWeight(getWeight() + 2.0);
}
/**
* Test
*/
public static void testDog() {
Dog d = new Dog("Woof", 2.0);
System.out.println(d.getName() == "Woof");
System.out.println(d.getWeight() == 2.0);
d.feed();
// The name is still the same but the weight increased by 2.0:
System.out.println(d.getName() == "Woof");
System.out.println(d.getWeight() == 4.0);
}
}

43
lab/lab5/Question5/Start.java Normal file
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/**
* Answer to question.
*
* # Question 4
*
* Q: Now that the Student class uses an animal as pet, can you still use a cat
* object as the pet of a student? Why or why not?
*
* A: Yes, you can. The Student class has a method getPet() that returns the pet
* which is Animal type.
*
* Q: Can you now use a dog object as the pet of a student? Why or why not?
*
* A: Yes, you can. But only attributes and methods definded in the Animal class
* can be accessed. When you do so, the Dog object will be converted to an
* Animal object. Assign a child object to a parent object is called upcasting
* in Java. Upcasting is implicit.
*
* # Question 5
*
* Q: Where are the name and weight of the bird stored? How?
*
* A: The Bird class has a private instance variable name and weight which are
* inherited from the Animal class.
*
* Q: Suppose a student has a bird as a pet. Can the student get the altitude of
* his pet?
*
* A: No. The student's pet is an Animal object. The Bird object is a subclass
* of Animal. getAltitude is only avaliable in Animal object. When we assign a
* Bird to an Animal variable, upcasting happend and only attributes and methods
* in the super class can be accessed.
*
*/
public class Start {
public static void main(String[] args) {
Cat.testCat();
Dog.testDog();
Student.testStudent();
Animal.testAnimal();
Bird.testBird();
}
}

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lab/lab5/Question5/Student.java Normal file
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/*
* Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
* Date: 2022/03/19
* Description: Student class
*/
public class Student {
/**
* Student's name
*/
private String name;
/**
* Student's pet
*/
private Animal pet;
/**
* Constructor
*/
public Student(String name, Animal pet) {
this.name = name;
this.pet = pet;
}
/**
* Getter for name
*
* @return String
*/
public String getName() {
return name;
}
/**
* Getter for pet
*
* @return Animal
*/
public Animal getPet() {
return pet;
}
/**
* Test
*/
public static void testStudent() {
Cat pet = new Cat("Tom", 1.0);
Student student = new Student("Walter", pet);
System.out.println(student.getName() == "Walter");
System.out.println(student.getPet() == pet);
System.out.println(student.getPet().getName() == "Tom");
System.out.println(student.getPet().getWeight() == 1.0);
Dog pet2 = new Dog("Jerry", 1.0);
Student student2 = new Student("Walter", pet2);
System.out.println(student2.getName() == "Walter");
System.out.println(student2.getPet() == pet2);
System.out.println(student2.getPet().getName() == "Jerry");
System.out.println(student2.getPet().getWeight() == 1.0);
Animal pet3 = new Animal("Unknown animal", 4.0);
Student student3 = new Student("Walter", pet3);
System.out.println(student3.getName() == "Walter");
System.out.println(student3.getPet() == pet3);
System.out.println(student3.getPet().getName() == "Unknown animal");
System.out.println(student3.getPet().getWeight() == 4.0);
Bird pet4 = new Bird("bird", 1.0, 39.0);
Student student4 = new Student("Walter", pet4);
System.out.println(student4.getName() == "Walter");
System.out.println(student4.getPet() == pet4);
System.out.println(student4.getPet().getName() == "bird");
System.out.println(student4.getPet().getWeight() == 1.0);
}
}