Add lab6

lab/lab6/Question1/Shape.java

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+/**
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007) Date: 2022/03/27
+ * Description: This is the Shape class.
+ */
+
+public class Shape {
+	private double x;
+	private double y;
+
+	/**
+	 * Constructor
+	 *
+	 * @param x the position of the center point of the shape
+	 * @param y the position of the center point of the shape
+	 */
+	public Shape(double x, double y) {
+		this.x = x;
+		this.y = y;
+	}
+
+	/**
+	 * Getter of x
+	 *
+	 * @return the position of the center point of the shape
+	 */
+	public double getX() {
+		return x;
+	}
+
+	/**
+	 * Getter of y
+	 *
+	 * @return the position of the center point of the shape
+	 */
+	public double getY() {
+		return y;
+	}
+
+	/**
+	 * The are of the shape
+	 *
+	 * @return the area of the shape
+	 */
+	public double area() {
+		System.out.println("An unknown shape has an unknown area!");
+		return -1.0;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testShape() {
+		Shape s = new Shape(1.0, 2.0);
+		System.out.println(s.getX() == 1.0);
+		System.out.println(s.getY() == 2.0);
+		System.out.println(s.area() == -1.0);
+	}
+}

lab/lab6/Question1/Start.java

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+public class Start {
+	public static void main(String[] args) {
+		Shape.testShape();
+	}
+}

lab/lab6/Question2/Circle.java

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+/**
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007) Date: 2022/03/27
+ * Description: This is the class of Circle.
+ */
+
+public class Circle extends Shape {
+	private double radius;
+
+	/**
+	 * Constructor of Circle.
+	 *
+	 * @param x      the x coordinate of the center of the circle
+	 * @param y      the y coordinate of the center of the circle
+	 * @param radius the radius of the circle
+	 */
+	public Circle(double x, double y, double radius) {
+		super(x, y);
+		this.radius = radius;
+	}
+
+	/**
+	 * Get the area of the circle.
+	 *
+	 * @return the area of the circle
+	 */
+	@Override
+	public double area() {
+		return Math.PI * radius * radius;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testCircle() {
+		Circle c1 = new Circle(1.0, 2.0, 3.0);
+		System.out.println(c1.getX() == 1.0);
+		System.out.println(c1.getY() == 2.0);
+		System.out.println(compare(c1.area(), 28.274333882308138));
+	}
+
+	/**
+	 * Compare two double numbers.
+	 *
+	 * @param a
+	 * @param b
+	 * @return true if a and b are equal, false otherwise
+	 */
+	public static boolean compare(double a, double b) {
+		return Math.abs(a - b) < 0.000001;
+	}
+}

lab/lab6/Question2/Shape.java

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+/**
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the Shape class.
+ */
+
+public class Shape {
+	private double x;
+	private double y;
+
+	/**
+	 * Constructor
+	 *
+	 * @param x the position of the center point of the shape
+	 * @param y the position of the center point of the shape
+	 */
+	public Shape(double x, double y) {
+		this.x = x;
+		this.y = y;
+	}
+
+	/**
+	 * Getter of x
+	 *
+	 * @return the position of the center point of the shape
+	 */
+	public double getX() {
+		return x;
+	}
+
+	/**
+	 * Getter of y
+	 *
+	 * @return the position of the center point of the shape
+	 */
+	public double getY() {
+		return y;
+	}
+	
+	/**
+	 * The are of the shape
+	 *
+	 * @return the area of the shape
+	 */
+	public double area() {
+		System.out.println("An unknown shape has an unknown area!");
+		return -1.0;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testShape() {
+		Shape s = new Shape(1.0, 2.0);
+		System.out.println(s.getX() == 1.0);
+		System.out.println(s.getY() == 2.0);
+		System.out.println(s.area() == -1.0);
+	}
+}

lab/lab6/Question2/Start.java

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+public class Start {
+	public static void main(String[] args) {
+		Shape.testShape();
+		Circle.testCircle();
+	}
+}

lab/lab6/Question3/Circle.java

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+/**
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007) Date: 2022/03/27
+ * Description: This is the class of Circle.
+ */
+
+public class Circle extends Shape {
+	private double radius;
+
+	/**
+	 * Constructor of Circle.
+	 *
+	 * @param x      the x coordinate of the center of the circle
+	 * @param y      the y coordinate of the center of the circle
+	 * @param radius the radius of the circle
+	 */
+	public Circle(double x, double y, double radius) {
+		super(x, y);
+		this.radius = radius;
+	}
+
+	/**
+	 * Get the area of the circle.
+	 *
+	 * @return the area of the circle
+	 */
+	@Override
+	public double area() {
+		return Math.PI * radius * radius;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testCircle() {
+		Circle c1 = new Circle(1.0, 2.0, 3.0);
+		System.out.println(c1.getX() == 1.0);
+		System.out.println(c1.getY() == 2.0);
+		System.out.println(compare(c1.area(), 28.274333882308138));
+	}
+
+	/**
+	 * Compare two double numbers.
+	 *
+	 * @param a
+	 * @param b
+	 * @return true if a and b are equal, false otherwise
+	 */
+	public static boolean compare(double a, double b) {
+		return Math.abs(a - b) < 0.000001;
+	}
+}

lab/lab6/Question3/Dot.java

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+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007).
+ * Date: 2022/03/27
+ * Description: This is the Dot class.
+ */
+
+public class Dot extends Shape {
+	/**
+	 * Constructor
+	 *
+	 * @param x double
+	 * @param y double
+	 */
+	public Dot(double x, double y) {
+		super(x, y);
+	}
+
+	/**
+	 * Override the area method. Dot has no (0.0) area.
+	 *
+	 * @return double
+	 */
+	@Override
+	public double area() {
+		return 0.0;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testDot() {
+		Dot d1 = new Dot(1.0, 2.0);
+		System.out.println(d1.getX() == 1.0);
+		System.out.println(d1.getY() == 2.0);
+		System.out.println(d1.area() == 0.0);
+	}
+}

lab/lab6/Question3/Shape.java

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+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the Shape class.
+ */
+
+public class Shape {
+	private double x;
+	private double y;
+
+	/**
+	 * Constructor
+	 *
+	 * @param x the position of the center point of the shape
+	 * @param y the position of the center point of the shape
+	 */
+	public Shape(double x, double y) {
+		this.x = x;
+		this.y = y;
+	}
+
+	/**
+	 * Getter of x
+	 *
+	 * @return the position of the center point of the shape
+	 */
+	public double getX() {
+		return x;
+	}
+
+	/**
+	 * Getter of y
+	 *
+	 * @return the position of the center point of the shape
+	 */
+	public double getY() {
+		return y;
+	}
+
+	/**
+	 * The are of the shape
+	 *
+	 * @return the area of the shape
+	 */
+	public double area() {
+		System.out.println("An unknown shape has an unknown area!");
+		return -1.0;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testShape() {
+		Shape s = new Shape(1.0, 2.0);
+		System.out.println(s.getX() == 1.0);
+		System.out.println(s.getY() == 2.0);
+		System.out.println(s.area() == -1.0);
+	}
+}

lab/lab6/Question3/Start.java

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+public class Start {
+	public static void main(String[] args) {
+		Shape.testShape();
+		Circle.testCircle();
+		Dot.testDot();
+	}
+}

lab/lab6/Question4/Circle.java

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+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the class of Circle.
+ */
+
+public class Circle extends Shape {
+	private double radius;
+
+	/**
+	 * Constructor of Circle.
+	 *
+	 * @param x      the x coordinate of the center of the circle
+	 * @param y      the y coordinate of the center of the circle
+	 * @param radius the radius of the circle
+	 */
+	public Circle(double x, double y, double radius) {
+		super(x, y);
+		this.radius = radius;
+	}
+
+	/**
+	 * Get the area of the circle.
+	 *
+	 * @return the area of the circle
+	 */
+	@Override
+	public double area() {
+		return Math.PI * radius * radius;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testCircle() {
+		Circle c1 = new Circle(1.0, 2.0, 3.0);
+		System.out.println(c1.getX() == 1.0);
+		System.out.println(c1.getY() == 2.0);
+		System.out.println(compare(c1.area(), 28.274333882308138));
+	}
+
+	/**
+	 * Compare two double numbers.
+	 *
+	 * @param a
+	 * @param b
+	 * @return true if a and b are equal, false otherwise
+	 */
+	public static boolean compare(double a, double b) {
+		return Math.abs(a - b) < 0.000001;
+	}
+}

lab/lab6/Question4/Dot.java

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+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007).
+ * Date: 2022/03/27
+ * Description: This is the Dot class.
+ */
+
+public class Dot extends Shape {
+	/**
+	 * Constructor
+	 *
+	 * @param x double
+	 * @param y double
+	 */
+	public Dot(double x, double y) {
+		super(x, y);
+	}
+
+	/**
+	 * Override the area method. Dot has no (0.0) area.
+	 *
+	 * @return double
+	 */
+	@Override
+	public double area() {
+		return 0.0;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testDot() {
+		Dot d1 = new Dot(1.0, 2.0);
+		System.out.println(d1.getX() == 1.0);
+		System.out.println(d1.getY() == 2.0);
+		System.out.println(d1.area() == 0.0);
+	}
+}

lab/lab6/Question4/Rectangle.java

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+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the Rectangle class.
+ */
+
+public class Rectangle extends Shape {
+	private double width;
+	private double height;
+
+	/**
+	 * Constructor
+	 * 
+	 * @param x      the x coordinate of the center of the rectangle
+	 * @param y      the y coordinate of the center of the rectangle
+	 * @param width  the width of the rectangle
+	 * @param length the length of the rectangle
+	 */
+	public Rectangle(double x, double y, double width, double length) {
+		super(x, y);
+		this.width = width;
+		this.height = length;
+	}
+
+	/**
+	 * Override the area method
+	 *
+	 * @return double
+	 */
+	@Override
+	public double area() {
+		return width * height;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testRectangle() {
+		Rectangle r1 = new Rectangle(1.0, 2.0, 3.0, 4.0);
+		System.out.println(r1.getX() == 1.0);
+		System.out.println(r1.getY() == 2.0);
+		System.out.println(r1.area() == 12.0);
+	}
+}

lab/lab6/Question4/Shape.java

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+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the Shape class.
+ */
+
+public class Shape {
+	private double x;
+	private double y;
+
+	/**
+	 * Constructor
+	 *
+	 * @param x the position of the center point of the shape
+	 * @param y the position of the center point of the shape
+	 */
+	public Shape(double x, double y) {
+		this.x = x;
+		this.y = y;
+	}
+
+	/**
+	 * Getter of x
+	 *
+	 * @return the position of the center point of the shape
+	 */
+	public double getX() {
+		return x;
+	}
+
+	/**
+	 * Getter of y
+	 *
+	 * @return the position of the center point of the shape
+	 */
+	public double getY() {
+		return y;
+	}
+
+	/**
+	 * The are of the shape
+	 *
+	 * @return the area of the shape
+	 */
+	public double area() {
+		System.out.println("An unknown shape has an unknown area!");
+		return -1.0;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testShape() {
+		Shape s = new Shape(1.0, 2.0);
+		System.out.println(s.getX() == 1.0);
+		System.out.println(s.getY() == 2.0);
+		System.out.println(s.area() == -1.0);
+	}
+}

lab/lab6/Question4/Square.java

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+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: Square class
+ */
+
+public class Square extends Rectangle {
+	/**
+	 * Constructor
+	 *
+	 * @param x    the x coordinate of the center of the square
+	 * @param y    the y coordinate of the center of the square
+	 * @param size
+	 */
+	public Square(double x, double y, double size) {
+		super(x, y, size, size);
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testSquare() {
+		Square s = new Square(1.0, 2.0, 3.0);
+		System.out.println(s.getX() == 1.0);
+		System.out.println(s.getY() == 2.0);
+		System.out.println(s.area() == 9.0);
+	}
+}

lab/lab6/Question4/Start.java

@@ -0,0 +1,9 @@
+public class Start {
+	public static void main(String[] args) {
+		Shape.testShape();
+		Circle.testCircle();
+		Dot.testDot();
+		Rectangle.testRectangle();
+		Square.testSquare();
+	}
+}

lab/lab6/Question5/Circle.java

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+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the class of Circle.
+ */
+
+public class Circle extends Shape {
+	private double radius;
+
+	/**
+	 * Constructor of Circle.
+	 *
+	 * @param x      the x coordinate of the center of the circle
+	 * @param y      the y coordinate of the center of the circle
+	 * @param radius the radius of the circle
+	 */
+	public Circle(double x, double y, double radius) {
+		super(x, y);
+		this.radius = radius;
+	}
+
+	/**
+	 * Get the area of the circle.
+	 *
+	 * @return the area of the circle
+	 */
+	@Override
+	public double area() {
+		return Math.PI * radius * radius;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testCircle() {
+		Circle c1 = new Circle(1.0, 2.0, 3.0);
+		System.out.println(c1.getX() == 1.0);
+		System.out.println(c1.getY() == 2.0);
+		System.out.println(compare(c1.area(), 28.274333882308138));
+	}
+
+	/**
+	 * Compare two double numbers.
+	 *
+	 * @param a
+	 * @param b
+	 * @return true if a and b are equal, false otherwise
+	 */
+	public static boolean compare(double a, double b) {
+		return Math.abs(a - b) < 0.000001;
+	}
+}

lab/lab6/Question5/Dot.java

@@ -0,0 +1,37 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007).
+ * Date: 2022/03/27
+ * Description: This is the Dot class.
+ */
+
+public class Dot extends Shape {
+	/**
+	 * Constructor
+	 *
+	 * @param x double
+	 * @param y double
+	 */
+	public Dot(double x, double y) {
+		super(x, y);
+	}
+
+	/**
+	 * Override the area method. Dot has no (0.0) area.
+	 *
+	 * @return double
+	 */
+	@Override
+	public double area() {
+		return 0.0;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testDot() {
+		Dot d1 = new Dot(1.0, 2.0);
+		System.out.println(d1.getX() == 1.0);
+		System.out.println(d1.getY() == 2.0);
+		System.out.println(d1.area() == 0.0);
+	}
+}

lab/lab6/Question5/ManyShapes.java

@@ -0,0 +1,56 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the class for the many shapes.
+ */
+
+import java.util.ArrayList;
+
+public class ManyShapes {
+	private ArrayList<Shape> allShapes;
+
+	/**
+	 * Constructor
+	 */
+	public ManyShapes() {
+		this.allShapes = new ArrayList<Shape>();
+	}
+
+	/**
+	 * addShape method takes a shape as argument and adds it to the arraylist.
+	 *
+	 * @param s the shape to be added
+	 */
+	public void addShape(Shape s) {
+		this.allShapes.add(s);
+	}
+
+	/**
+	 * listAllShapes methods prints on the screen the area of each shape in the
+	 * arraylist, one by one, using a loop. For example, if the arraylist currently
+	 * contains a Square object of size 5 and a Dot object the the listAllShapes
+	 * methods should print:
+	 *
+	 * Shape has area 25.0
+	 *
+	 * Shape has area 0.0
+	 */
+	public void listAllShapes() {
+		for (Shape s : this.allShapes) {
+			System.out.println("Shape has area " + s.area());
+		}
+	}
+
+	/**
+	 * Test.
+	 */
+	public static void testManyShapes() {
+		ManyShapes m = new ManyShapes();
+		m.addShape(new Circle(1.2, 3.4, 4.0)); // Upcast from Circle to Shape.
+		m.addShape(new Dot(1.2, 3.4)); // Upcast from Dot to Shape.
+		m.addShape(new Rectangle(1.2, 3.4, 4.0, 5.0)); // Upcast from Rectangle to Shape.
+		m.addShape(new Shape(1.2, 3.4));
+		m.addShape(new Square(1.2, 3.4, 5.0)); // Upcast from Square to Shape.
+		m.listAllShapes();
+	}
+}

lab/lab6/Question5/Rectangle.java

@@ -0,0 +1,44 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the Rectangle class.
+ */
+
+public class Rectangle extends Shape {
+	private double width;
+	private double height;
+
+	/**
+	 * Constructor
+	 * 
+	 * @param x      the x coordinate of the center of the rectangle
+	 * @param y      the y coordinate of the center of the rectangle
+	 * @param width  the width of the rectangle
+	 * @param length the length of the rectangle
+	 */
+	public Rectangle(double x, double y, double width, double length) {
+		super(x, y);
+		this.width = width;
+		this.height = length;
+	}
+
+	/**
+	 * Override the area method
+	 *
+	 * @return double
+	 */
+	@Override
+	public double area() {
+		return width * height;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testRectangle() {
+		Rectangle r1 = new Rectangle(1.0, 2.0, 3.0, 4.0);
+		System.out.println(r1.getX() == 1.0);
+		System.out.println(r1.getY() == 2.0);
+		System.out.println(r1.area() == 12.0);
+	}
+}

lab/lab6/Question5/Shape.java

@@ -0,0 +1,59 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the Shape class.
+ */
+
+public class Shape {
+	private double x;
+	private double y;
+
+	/**
+	 * Constructor
+	 *
+	 * @param x the position of the center point of the shape
+	 * @param y the position of the center point of the shape
+	 */
+	public Shape(double x, double y) {
+		this.x = x;
+		this.y = y;
+	}
+
+	/**
+	 * Getter of x
+	 *
+	 * @return the position of the center point of the shape
+	 */
+	public double getX() {
+		return x;
+	}
+
+	/**
+	 * Getter of y
+	 *
+	 * @return the position of the center point of the shape
+	 */
+	public double getY() {
+		return y;
+	}
+
+	/**
+	 * The are of the shape
+	 *
+	 * @return the area of the shape
+	 */
+	public double area() {
+		System.out.println("An unknown shape has an unknown area!");
+		return -1.0;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testShape() {
+		Shape s = new Shape(1.0, 2.0);
+		System.out.println(s.getX() == 1.0);
+		System.out.println(s.getY() == 2.0);
+		System.out.println(s.area() == -1.0);
+	}
+}

lab/lab6/Question5/Square.java

@@ -0,0 +1,28 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: Square class
+ */
+
+public class Square extends Rectangle {
+	/**
+	 * Constructor
+	 *
+	 * @param x    the x coordinate of the center of the square
+	 * @param y    the y coordinate of the center of the square
+	 * @param size
+	 */
+	public Square(double x, double y, double size) {
+		super(x, y, size, size);
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testSquare() {
+		Square s = new Square(1.0, 2.0, 3.0);
+		System.out.println(s.getX() == 1.0);
+		System.out.println(s.getY() == 2.0);
+		System.out.println(s.area() == 9.0);
+	}
+}

lab/lab6/Question5/Start.java

@@ -0,0 +1,10 @@
+public class Start {
+	public static void main(String[] args) {
+		Shape.testShape();
+		Circle.testCircle();
+		Dot.testDot();
+		Rectangle.testRectangle();
+		Square.testSquare();
+		ManyShapes.testManyShapes();
+	}
+}

lab/lab6/Question6/Circle.java

@@ -0,0 +1,52 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the class of Circle.
+ */
+
+public class Circle extends Shape {
+	private double radius;
+
+	/**
+	 * Constructor of Circle.
+	 *
+	 * @param x      the x coordinate of the center of the circle
+	 * @param y      the y coordinate of the center of the circle
+	 * @param radius the radius of the circle
+	 */
+	public Circle(double x, double y, double radius) {
+		super(x, y);
+		this.radius = radius;
+	}
+
+	/**
+	 * Get the area of the circle.
+	 *
+	 * @return the area of the circle
+	 */
+	@Override
+	public double area() {
+		return Math.PI * radius * radius;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testCircle() {
+		Circle c1 = new Circle(1.0, 2.0, 3.0);
+		System.out.println(c1.getX() == 1.0);
+		System.out.println(c1.getY() == 2.0);
+		System.out.println(compare(c1.area(), 28.274333882308138));
+	}
+
+	/**
+	 * Compare two double numbers.
+	 *
+	 * @param a
+	 * @param b
+	 * @return true if a and b are equal, false otherwise
+	 */
+	public static boolean compare(double a, double b) {
+		return Math.abs(a - b) < 0.000001;
+	}
+}

lab/lab6/Question6/Dot.java

@@ -0,0 +1,37 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007).
+ * Date: 2022/03/27
+ * Description: This is the Dot class.
+ */
+
+public class Dot extends Shape {
+	/**
+	 * Constructor
+	 *
+	 * @param x double
+	 * @param y double
+	 */
+	public Dot(double x, double y) {
+		super(x, y);
+	}
+
+	/**
+	 * Override the area method. Dot has no (0.0) area.
+	 *
+	 * @return double
+	 */
+	@Override
+	public double area() {
+		return 0.0;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testDot() {
+		Dot d1 = new Dot(1.0, 2.0);
+		System.out.println(d1.getX() == 1.0);
+		System.out.println(d1.getY() == 2.0);
+		System.out.println(d1.area() == 0.0);
+	}
+}

lab/lab6/Question6/ManyShapes.java

@@ -0,0 +1,70 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the class for the many shapes.
+ */
+
+import java.util.ArrayList;
+
+public class ManyShapes {
+	private ArrayList<Shape> allShapes;
+
+	/**
+	 * Constructor
+	 */
+	public ManyShapes() {
+		this.allShapes = new ArrayList<Shape>();
+	}
+
+	/**
+	 * addShape method takes a shape as argument and adds it to the arraylist.
+	 *
+	 * @param s the shape to be added
+	 */
+	public void addShape(Shape s) {
+		this.allShapes.add(s);
+	}
+
+	/**
+	 * listAllShapes methods print out both the area and the type for each shape in
+	 * the arraylist. For example, if the arraylist currently contains a Square
+	 * object of size 5 and a Dot object the the listAllShapes method should print:
+	 *
+	 * Shape has area 25.0
+	 *
+	 * Shape has area 0.0
+	 */
+	public void listAllShapes() {
+		for (Shape s : this.allShapes) {
+			String type = "";
+			if (s instanceof Square) {
+				type = "Square";
+			} else if (s instanceof Dot) {
+				type = "Dot";
+			} else if (s instanceof Circle) {
+				type = "Circle";
+			} else if (s instanceof Rectangle) {
+				type = "Rectangle";
+			} else if (s instanceof Shape) {
+				type = "Shape";
+			} else if (s instanceof Square) {
+				type = "Square";
+			}
+
+			System.out.println(String.format("%s has area %f", type, s.area()));
+		}
+	}
+
+	/**
+	 * Test.
+	 */
+	public static void testManyShapes() {
+		ManyShapes m = new ManyShapes();
+		m.addShape(new Circle(1.2, 3.4, 4.0)); // Upcast from Circle to Shape.
+		m.addShape(new Dot(1.2, 3.4)); // Upcast from Dot to Shape.
+		m.addShape(new Rectangle(1.2, 3.4, 4.0, 5.0)); // Upcast from Rectangle to Shape.
+		m.addShape(new Shape(1.2, 3.4));
+		m.addShape(new Square(1.2, 3.4, 5.0)); // Upcast from Square to Shape.
+		m.listAllShapes();
+	}
+}

lab/lab6/Question6/Rectangle.java

@@ -0,0 +1,44 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the Rectangle class.
+ */
+
+public class Rectangle extends Shape {
+	private double width;
+	private double height;
+
+	/**
+	 * Constructor
+	 * 
+	 * @param x      the x coordinate of the center of the rectangle
+	 * @param y      the y coordinate of the center of the rectangle
+	 * @param width  the width of the rectangle
+	 * @param length the length of the rectangle
+	 */
+	public Rectangle(double x, double y, double width, double length) {
+		super(x, y);
+		this.width = width;
+		this.height = length;
+	}
+
+	/**
+	 * Override the area method
+	 *
+	 * @return double
+	 */
+	@Override
+	public double area() {
+		return width * height;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testRectangle() {
+		Rectangle r1 = new Rectangle(1.0, 2.0, 3.0, 4.0);
+		System.out.println(r1.getX() == 1.0);
+		System.out.println(r1.getY() == 2.0);
+		System.out.println(r1.area() == 12.0);
+	}
+}

lab/lab6/Question6/Shape.java

@@ -0,0 +1,59 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the Shape class.
+ */
+
+public class Shape {
+	private double x;
+	private double y;
+
+	/**
+	 * Constructor
+	 *
+	 * @param x the position of the center point of the shape
+	 * @param y the position of the center point of the shape
+	 */
+	public Shape(double x, double y) {
+		this.x = x;
+		this.y = y;
+	}
+
+	/**
+	 * Getter of x
+	 *
+	 * @return the position of the center point of the shape
+	 */
+	public double getX() {
+		return x;
+	}
+
+	/**
+	 * Getter of y
+	 *
+	 * @return the position of the center point of the shape
+	 */
+	public double getY() {
+		return y;
+	}
+
+	/**
+	 * The are of the shape
+	 *
+	 * @return the area of the shape
+	 */
+	public double area() {
+		System.out.println("An unknown shape has an unknown area!");
+		return -1.0;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testShape() {
+		Shape s = new Shape(1.0, 2.0);
+		System.out.println(s.getX() == 1.0);
+		System.out.println(s.getY() == 2.0);
+		System.out.println(s.area() == -1.0);
+	}
+}

lab/lab6/Question6/Square.java

@@ -0,0 +1,28 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: Square class
+ */
+
+public class Square extends Rectangle {
+	/**
+	 * Constructor
+	 *
+	 * @param x    the x coordinate of the center of the square
+	 * @param y    the y coordinate of the center of the square
+	 * @param size
+	 */
+	public Square(double x, double y, double size) {
+		super(x, y, size, size);
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testSquare() {
+		Square s = new Square(1.0, 2.0, 3.0);
+		System.out.println(s.getX() == 1.0);
+		System.out.println(s.getY() == 2.0);
+		System.out.println(s.area() == 9.0);
+	}
+}

lab/lab6/Question6/Start.java

@@ -0,0 +1,10 @@
+public class Start {
+	public static void main(String[] args) {
+		Shape.testShape();
+		Circle.testCircle();
+		Dot.testDot();
+		Rectangle.testRectangle();
+		Square.testSquare();
+		ManyShapes.testManyShapes();
+	}
+}

lab/lab6/Question7/Circle.java

@@ -0,0 +1,60 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the class of Circle.
+ */
+
+public class Circle extends Shape {
+	private double radius;
+
+	/**
+	 * Constructor of Circle.
+	 *
+	 * @param x      the x coordinate of the center of the circle
+	 * @param y      the y coordinate of the center of the circle
+	 * @param radius the radius of the circle
+	 */
+	public Circle(double x, double y, double radius) {
+		super(x, y);
+		this.radius = radius;
+	}
+
+	/**
+	 * Get the area of the circle.
+	 *
+	 * @return the area of the circle
+	 */
+	@Override
+	public double area() {
+		return Math.PI * radius * radius;
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testCircle() {
+		Circle c1 = new Circle(1.0, 2.0, 3.0);
+		System.out.println(c1.getX() == 1.0);
+		System.out.println(c1.getY() == 2.0);
+		System.out.println(compare(c1.area(), 28.274333882308138));
+	}
+
+	/**
+	 * Compare two double numbers.
+	 *
+	 * @param a
+	 * @param b
+	 * @return true if a and b are equal, false otherwise
+	 */
+	public static boolean compare(double a, double b) {
+		return Math.abs(a - b) < 0.000001;
+	}
+
+	/**
+	 * toString
+	 */
+	@Override
+	public String toString() {
+		return this.getClass().getName() + " has area " + area();
+	}
+}

lab/lab6/Question7/Dot.java

@@ -0,0 +1,45 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007).
+ * Date: 2022/03/27
+ * Description: This is the Dot class.
+ */
+
+public class Dot extends Shape {
+	/**
+	 * Constructor
+	 *
+	 * @param x double
+	 * @param y double
+	 */
+	public Dot(double x, double y) {
+		super(x, y);
+	}
+
+	/**
+	 * Override the area method. Dot has no (0.0) area.
+	 *
+	 * @return double
+	 */
+	@Override
+	public double area() {
+		return 0.0;
+	}
+
+	/**
+	 * toString
+	 */
+	@Override
+	public String toString() {
+		return this.getClass().getName() + " has area " + area();
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testDot() {
+		Dot d1 = new Dot(1.0, 2.0);
+		System.out.println(d1.getX() == 1.0);
+		System.out.println(d1.getY() == 2.0);
+		System.out.println(d1.area() == 0.0);
+	}
+}

lab/lab6/Question7/ManyShapes.java

@@ -0,0 +1,55 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the class for the many shapes.
+ */
+
+import java.util.ArrayList;
+
+public class ManyShapes {
+	private ArrayList<Shape> allShapes;
+
+	/**
+	 * Constructor
+	 */
+	public ManyShapes() {
+		this.allShapes = new ArrayList<Shape>();
+	}
+
+	/**
+	 * addShape method takes a shape as argument and adds it to the arraylist.
+	 *
+	 * @param s the shape to be added
+	 */
+	public void addShape(Shape s) {
+		this.allShapes.add(s);
+	}
+
+	/**
+	 * listAllShapes methods print out both the area and the type for each shape in
+	 * the arraylist. For example, if the arraylist currently contains a Square
+	 * object of size 5 and a Dot object the the listAllShapes method should print:
+	 *
+	 * Shape has area 25.0
+	 *
+	 * Shape has area 0.0
+	 */
+	public void listAllShapes() {
+		for (Shape s : this.allShapes) {
+			System.out.println(s);
+		}
+	}
+
+	/**
+	 * Test.
+	 */
+	public static void testManyShapes() {
+		ManyShapes m = new ManyShapes();
+		m.addShape(new Circle(1.2, 3.4, 4.0)); // Upcast from Circle to Shape.
+		m.addShape(new Dot(1.2, 3.4)); // Upcast from Dot to Shape.
+		m.addShape(new Rectangle(1.2, 3.4, 4.0, 5.0)); // Upcast from Rectangle to Shape.
+		m.addShape(new Shape(1.2, 3.4));
+		m.addShape(new Square(1.2, 3.4, 5.0)); // Upcast from Square to Shape.
+		m.listAllShapes();
+	}
+}

lab/lab6/Question7/Rectangle.java

@@ -0,0 +1,52 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the Rectangle class.
+ */
+
+public class Rectangle extends Shape {
+	private double width;
+	private double height;
+
+	/**
+	 * Constructor
+	 * 
+	 * @param x      the x coordinate of the center of the rectangle
+	 * @param y      the y coordinate of the center of the rectangle
+	 * @param width  the width of the rectangle
+	 * @param length the length of the rectangle
+	 */
+	public Rectangle(double x, double y, double width, double length) {
+		super(x, y);
+		this.width = width;
+		this.height = length;
+	}
+
+	/**
+	 * Override the area method
+	 *
+	 * @return double
+	 */
+	@Override
+	public double area() {
+		return width * height;
+	}
+
+	/**
+	 * toString
+	 */
+	@Override
+	public String toString() {
+		return this.getClass().getName() + " has area " + area();
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testRectangle() {
+		Rectangle r1 = new Rectangle(1.0, 2.0, 3.0, 4.0);
+		System.out.println(r1.getX() == 1.0);
+		System.out.println(r1.getY() == 2.0);
+		System.out.println(r1.area() == 12.0);
+	}
+}

lab/lab6/Question7/Shape.java

@@ -0,0 +1,66 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: This is the Shape class.
+ */
+
+public class Shape {
+	private double x;
+	private double y;
+
+	/**
+	 * Constructor
+	 *
+	 * @param x the position of the center point of the shape
+	 * @param y the position of the center point of the shape
+	 */
+	public Shape(double x, double y) {
+		this.x = x;
+		this.y = y;
+	}
+
+	/**
+	 * Getter of x
+	 *
+	 * @return the position of the center point of the shape
+	 */
+	public double getX() {
+		return x;
+	}
+
+	/**
+	 * Getter of y
+	 *
+	 * @return the position of the center point of the shape
+	 */
+	public double getY() {
+		return y;
+	}
+
+	/**
+	 * The are of the shape
+	 *
+	 * @return the area of the shape
+	 */
+	public double area() {
+		System.out.println("An unknown shape has an unknown area!");
+		return -1.0;
+	}
+
+	/**
+	 * toString method
+	 */
+	public String toString() {
+		return this.getClass().getName() + " has area " + area();
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testShape() {
+		Shape s = new Shape(1.0, 2.0);
+		System.out.println(s.getX() == 1.0);
+		System.out.println(s.getY() == 2.0);
+		System.out.println(s.area() == -1.0);
+	}
+}

lab/lab6/Question7/Square.java

@@ -0,0 +1,36 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022/03/27
+ * Description: Square class
+ */
+
+public class Square extends Rectangle {
+	/**
+	 * Constructor
+	 *
+	 * @param x    the x coordinate of the center of the square
+	 * @param y    the y coordinate of the center of the square
+	 * @param size
+	 */
+	public Square(double x, double y, double size) {
+		super(x, y, size, size);
+	}
+
+	/**
+	 * toString
+	 */
+	@Override
+	public String toString() {
+		return this.getClass().getName() + " has area " + area();
+	}
+
+	/**
+	 * Test
+	 */
+	public static void testSquare() {
+		Square s = new Square(1.0, 2.0, 3.0);
+		System.out.println(s.getX() == 1.0);
+		System.out.println(s.getY() == 2.0);
+		System.out.println(s.area() == 9.0);
+	}
+}

lab/lab6/Question7/Start.java

@@ -0,0 +1,10 @@
+public class Start {
+	public static void main(String[] args) {
+		Shape.testShape();
+		Circle.testCircle();
+		Dot.testDot();
+		Rectangle.testRectangle();
+		Square.testSquare();
+		ManyShapes.testManyShapes();
+	}
+}