分层练习设计

w5/A_Circlew5.java

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+public class A_Circlew5 extends A_Graphic {
+    @Override
+    public void draw() {
+        System.out.println("绘制一个圆形");
+    }
+}

w5/A_Graphic.java

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+public class A_Graphic {
+    public void draw() {
+        System.out.println("绘制一个图形");
+    }
+}

w5/A_Main1.java

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+public class A_Main1 {public static void drawGraphic(A_Graphic g) {
+    g.draw();
+}
+
+    public static void main(String[] args) {
+        A_Graphic graphic = new A_Graphic();
+        A_Circlew5 circle = new A_Circlew5();
+        A_Rectanglew5 rectangle = new A_Rectanglew5();
+
+        drawGraphic(graphic);
+        drawGraphic(circle);
+        drawGraphic(rectangle);
+    }
+}
+

w5/A_Rectanglew5.java

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+public class A_Rectanglew5 extends A_Graphic {
+    @Override
+    public void draw() {
+        System.out.println("绘制一个矩形");
+    }
+}

w5/Bike.java

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+public class Bike extends Vehicle {
+    @Override
+    public void run() {
+        System.out.println("自行车在自行车道上骑行");
+    }
+}

w5/Car.java

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+public class Car extends Vehicle {
+    @Override
+    public void run() {
+        System.out.println("汽车在公路上行驶");
+    }
+}

w5/Main2.java

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+public class Main2 {
+    public static void main(String[] args) {
+        Vehicle[] vehicles = new Vehicle[3];
+        vehicles[0] = new Car();
+        vehicles[1] = new Bike();
+        vehicles[2] = new Truck();
+
+        for (Vehicle v : vehicles) {
+            v.run();
+        }
+    }
+}

w5/Truck.java

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+public class Truck extends Vehicle {
+    @Override
+    public void run() {
+        System.out.println("卡车在高速上运输货物");
+    }
+}

w5/Vehicle.java

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+public abstract class Vehicle {
+    public abstract void run();
+}