w5

w5/MainFiveAdvanced.java

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+public class MainFiveAdvanced {
+    public abstract static class Vehicle {
+        public abstract void run();
+    }
+
+    public static class Car extends Vehicle {
+        public void run() {
+            System.out.println("This is car running!");
+        }
+    }
+
+    public static class Bike extends Vehicle {
+        public void run() {
+            System.out.println("This is bike running!");
+        }
+    }
+
+    public static class Truck extends Vehicle {
+        public void run() {
+            System.out.println("This is truck running!");
+        }
+    }
+
+    public static void main(String[] args) {
+        Vehicle[] vehicles = new Vehicle[5];
+
+        vehicles[0] = new Car();
+        vehicles[1] = new Bike();
+        vehicles[2] = new Truck();
+        vehicles[3] = new Car();
+        vehicles[4] = new Truck();
+
+        for (Vehicle vehicle : vehicles) {
+            vehicle.run();
+        }
+    }
+}

w5/MainFiveBasic.java

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+public class MainFiveBasic {
+    public static abstract class Shape {
+        public abstract void draw();
+    }
+
+    public static class Circle extends Shape {
+        private final Double radius;
+
+        public Circle(Double radius) {
+            this.radius = radius;
+        }
+
+        public void draw() {
+            System.out.println("Drawing a circle of radius " + radius);
+        }
+    }
+
+    public static class Rectangle extends Shape {
+        private final Double side1;
+        private final Double side2;
+
+        public Rectangle(Double side1, Double side2) {
+            this.side1 = side1;
+            this.side2 = side2;
+        }
+
+        public void draw() {
+            System.out.println("Drawing a rectangle of " + side1 + " * " + side2);
+        }
+    }
+
+    public static void drawShape(Shape s) {
+        s.draw();
+    }
+
+    public static void main(String[] args) {
+        Shape circle = new Circle(1.23);
+        Shape rectangle = new Rectangle(1.23, 4.56);
+
+        drawShape(circle);
+        drawShape(rectangle);
+    }
+}

w5/usage.md

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+# 使用
+
+```console
+$ javac MainFiveBasic.java && java MainFiveBasic
+Drawing a circle of radius 1.23
+Drawing a rectangle of 1.23 * 4.56
+```
+
+```console
+$ javac MainFiveAdvanced.java && java MainFiveAdvanced
+This is car running!
+This is bike running!
+This is truck running!
+This is car running!
+This is truck running!
+```