上传文件至 'W4'

W4/Circle.java

@@ -0,0 +1,14 @@
+// 文件名：Circle.java
+public class Circle extends Shape {
+    private double radius; // 半径
+
+    public Circle(double radius) {
+        this.radius = radius;
+    }
+
+    // 实现父类的抽象方法
+    @Override
+    public double getArea() {
+        return Math.PI * radius * radius;
+    }
+}

W4/Main.java

@@ -0,0 +1,21 @@
+// 文件名：Main.java
+public class Main {
+    public static void main(String[] args) {
+        // 创建具体图形对象
+        Shape c = new Circle(5);
+        Shape r = new Rectangle(4, 6);
+        Shape t = new Triangle(3, 8);
+
+        // 使用工具类统一处理
+        ShapeUtil util = new ShapeUtil();
+
+        System.out.print("圆形 -> ");
+        util.printArea(c);
+
+        System.out.print("矩形 -> ");
+        util.printArea(r);
+
+        System.out.print("三角形 -> ");
+        util.printArea(t);
+    }
+}

W4/Rectangle.java

@@ -0,0 +1,15 @@
+// 文件名：Rectangle.java
+public class Rectangle extends Shape {
+    private double width;
+    private double height;
+
+    public Rectangle(double width, double height) {
+        this.width = width;
+        this.height = height;
+    }
+
+    @Override
+    public double getArea() {
+        return width * height;
+    }
+}

W4/Shape.java

@@ -0,0 +1,4 @@
+public abstract class Shape {
+    public abstract double getArea();
+
+}

W4/ShapeUtil.java

@@ -0,0 +1,5 @@
+public class ShapeUtil {
+    public void printArea(Shape shape) {
+        System.out.println("该图形的面积是: " + shape.getArea());
+    }
+}