添加W3

W3/Circle.java

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+public class Circle extends Shape {
+    private double radius;
+
+    public Circle(double radius) {
+        this.radius = radius;
+    }
+
+    @Override
+    public double getArea() {
+        return Math.PI * radius * radius;
+    }
+}

W3/Rectangle.java

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+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;
+    }
+}

W3/Shape.java

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+public abstract class Shape {
+    // 抽象方法：计算图形面积
+    public abstract double getArea();
+}

W3/ShapeUtil.java

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+public class ShapeUtil {
+    public static void printArea(Shape shape) {
+        if (shape == null) {
+            System.out.println("图形对象不能为空！");
+            return;
+        }
+        System.out.printf("图形面积为：%.2f%n", shape.getArea());
+    }
+}

W3/Test.java

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+public class Test {
+    public static void main(String[] args) {
+        // 创建不同图形对象
+        Shape circle = new Circle(3);
+        Shape rect = new Rectangle(4, 5);
+        Shape triangle = new Triangle(3, 4, 5);
+
+        // 统一调用工具类打印面积
+        System.out.println("圆形：");
+        ShapeUtil.printArea(circle);
+
+        System.out.println("矩形：");
+        ShapeUtil.printArea(rect);
+
+        System.out.println("三角形：");
+        ShapeUtil.printArea(triangle);
+    }
+}

W3/Triangle.java

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+public class Triangle extends Shape {
+    private double a, b, c;
+
+    public Triangle(double a, double b, double c) {
+        this.a = a;
+        this.b = b;
+        this.c = c;
+    }
+
+    @Override
+    public double getArea() {
+        double p = (a + b + c) / 2;
+        return Math.sqrt(p * (p - a) * (p - b) * (p - c));
+    }
+}

desktop.ini

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+[LocalizedFileNames]
+QQ20260327-221432.png=@QQ20260327-221432.png,0