lab8 finished

lab/lab8/Question6/Circle.java

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+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-14
+ * Description: Circle class inherit from Shape class
+ */
+
+public class Circle extends Shape {
+	private double radius;
+
+	/**
+	 * Constructor.
+	 *
+	 * @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;
+	}
+
+	/**
+	 * Calculates the area of the circle.
+	 *
+	 * @return the area of the circle
+	 */
+	@Override
+	public double area() {
+		return Math.PI * radius * radius;
+	}
+
+	/**
+	 * Resizing a circle cahnges its radius to be newRadius.
+	 *
+	 * @param newRadius
+	 */
+	@Override
+	public void resize(double newRadius) {
+		radius = newRadius;
+	}
+
+	/**
+	 * Test.
+	 */
+	public static void testCircle() {
+		Circle c = new Circle(1.2, 3.4, 4.0);
+		// getX, getY, and move are inherited from Shape.
+		// area and resize come from Circle itself.
+		System.out.println(c.getX() == 1.2);
+		System.out.println(c.getY() == 3.4);
+		System.out.println(c.area() == Math.PI * 16.0);
+		// Move the circle. The area does not change.
+		c.move(7.8, 9.0);
+		System.out.println(c.getX() == 9.0);
+		System.out.println(c.getY() == 12.4);
+		System.out.println(c.area() == Math.PI * 16.0);
+		// Resize the circle. The area changes but not the position.
+		c.resize(8.0);
+		System.out.println(c.getX() == 9.0);
+		System.out.println(c.getY() == 12.4);
+		System.out.println(c.area() == Math.PI * 64.0);
+	}
+}