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Labs/Lab5/Lab5_2230026071/Question4/src/Animal.java

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+
+public class Animal {
+	//instance variables
+	private String name;
+	private double weight;
+	
+	//constructor
+	public Animal (String name, double weight) {
+		this.name = name;
+		this.weight = weight;
+	}
+	
+	//methods
+	public String getName() {return this.name;}
+	
+	public double getWeight() {return this.weight;}
+	
+	public void setWeight (double weight) {this.weight = weight;}
+	
+	//test
+	public static void testAnimal() {
+		Animal a = new Animal("Blob", 2.0);
+		System.out.println(a.getName() == "Blob");
+		System.out.println(a.getWeight() == 2.0);
+		a.setWeight(3.0);
+		System.out.println(a.getName() == "Blob");
+		System.out.println(a.getWeight() == 3.0);
+		}
+
+	
+}

Labs/Lab5/Lab5_2230026071/Question4/src/Cat.java

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+
+public class Cat extends Animal {
+	//constructor
+	public Cat (String name, double weight) {
+		super(name, weight);
+	}
+	
+	//method
+	public void feed() {super.setWeight(getWeight() + 1.0);}
+	
+	//test
+	public static void testCat() {
+		Cat c = new Cat("Meow", 2.0);
+		// The getName and getWeight methods are inherited from Animal.
+		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);
+		// The setWeight method is inherited too.
+		c.setWeight(2.0);
+		System.out.println(c.getName() == "Meow");
+		System.out.println(c.getWeight() == 2.0);
+		}
+
+}

Labs/Lab5/Lab5_2230026071/Question4/src/Dog.java

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+
+public class Dog extends Animal {
+	//constructor
+	public Dog (String name, double weight) {
+		super(name, weight);
+	}
+	
+	//method
+	public void feed() {super.setWeight(getWeight() + 2.0);}
+	
+	//test
+	public static void testDog() {
+		Dog d = new Dog("Woof", 2.0);
+		// The getName and getWeight methods are inherited from Animal.
+		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);
+		// The setWeight method is inherited too.
+		d.setWeight(2.0);
+		System.out.println(d.getName() == "Woof");
+		System.out.println(d.getWeight() == 2.0);
+		}
+
+}

Labs/Lab5/Lab5_2230026071/Question4/src/Start.java

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+
+public class Start {
+
+	//no, because cat inherits animal and the student's pet type are undetermined
+	public static void main(String[] args) {
+		// Unit tests
+		// !!! Codes here written by your self !!!
+		// Partial codes of System tests, to test both classes together.
+		Cat c = new Cat("Meow", 2.0);
+		Student s0 = new Student("Philippe", c);
+		System.out.println(s0.getPet().getName() == "Meow");
+		System.out.println(s0.getPet().getWeight() == 2.0);
+		s0.getPet().setWeight(3.0);
+		System.out.println(s0.getPet().getName() == "Meow");
+		System.out.println(s0.getPet().getWeight() == 3.0);
+		// Creating a new student with a dog as pet:
+		Dog d = new Dog("Woof", 2.0);
+		Student s1 = new Student("Mr. Li", d);
+		System.out.println(s1.getPet().getName() == "Woof");
+		System.out.println(s1.getPet().getWeight() == 2.0);
+		s1.getPet().setWeight(3.0);
+		System.out.println(s1.getPet().getName() == "Woof");
+		System.out.println(s1.getPet().getWeight() == 3.0);
+		// We can now also use an Animal object as a pet:
+		Animal a = new Animal("Blob", 5.0);
+		Student s2 = new Student("Ms. Chen", a);
+		System.out.println(s2.getPet().getName() == "Blob");
+		System.out.println(s2.getPet().getWeight() == 5.0);
+		s2.getPet().setWeight(3.0);
+		System.out.println(s2.getPet().getName() == "Blob");
+		System.out.println(s2.getPet().getWeight() == 3.0);
+		}
+
+}

Labs/Lab5/Lab5_2230026071/Question4/src/Student.java

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+
+public class Student {
+	//instance variables
+	private String name;
+	private Animal pet;
+	
+	//constructor
+	public Student(String name, Animal pet) {
+		this.name = name;
+		this.pet = pet;
+	}
+	
+	//methods
+	public String getName() {return this.name;}
+	
+	public Animal getPet() {return this.pet;}
+	
+	//test
+	public static void testStudent() {
+		Cat c = new Cat("Meow", 2.0);
+		Student s0 = new Student("Philippe", c);
+		System.out.println(s0.getName() == "Philippe");
+		System.out.println(s0.getPet() == c);
+		// Creating a new student with a dog as pet:
+		Dog d = new Dog("Woof", 2.0);
+		Student s1 = new Student("Mr. Li", d);
+		System.out.println(s1.getName() == "Mr. Li");
+		System.out.println(s1.getPet() == d);
+		// We can now also use an Animal object as a pet:
+		Animal a = new Animal("Blob", 5.0);
+		Student s2 = new Student("Ms. Chen", a);
+		System.out.println(s2.getName() == "Ms. Chen");
+		System.out.println(s2.getPet() == a);
+		}
+
+}