w5

README.md

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+# java
+

w1/HelloWorld.java

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+HelloWorld

w5/ShapeAreaCalculator.java

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+
+abstract class Shape {
+
+    public abstract double getArea();
+}
+class Circle extends Shape {
+    private double radius;
+    public Circle(double radius) {
+        if (radius <= 0) {
+            throw new IllegalArgumentException("半径必须为正数");
+        }
+        this.radius = radius;
+    }
+    @Override
+    public double getArea() {
+        return Math.PI * radius * radius;
+    }
+}
+class Rectangle extends Shape {
+    private double width;
+    private double height;
+    public Rectangle(double width, double height) {
+        if (width <= 0 || height <= 0) {
+            throw new IllegalArgumentException("宽和高必须为正数");
+        }
+        this.width = width;
+        this.height = height;
+    }
+
+    @Override
+    public double getArea() {
+        return width * height;
+    }
+}
+class Triangle extends Shape {
+    private double a;
+    private double b;
+    private double c;
+    public Triangle(double a, double b, double c) {
+        if (a <= 0 || b <= 0 || c <= 0) {
+            throw new IllegalArgumentException("边长必须为正数");
+        }
+        if (a + b <= c || a + c <= b || b + c <= a) {
+            throw new IllegalArgumentException("三边不满足三角形构成条件");
+        }
+        this.a = a;
+        this.b = b;
+        this.c = c;
+    }
+    @Override
+    public double getArea() {
+        double s = (a + b + c) / 2;
+        return Math.sqrt(s * (s - a) * (s - b) * (s - c));
+    }
+}
+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：%.2f%n", shape.getArea());
+    }
+}
+public class ShapeAreaCalculator {
+    public static void main(String[] args) {
+        try {
+            Shape circle = new Circle(3);
+            System.out.print("圆形：");
+            ShapeUtil.printArea(circle);
+            Shape rectangle = new Rectangle(4, 5);
+            System.out.print("矩形：");
+            ShapeUtil.printArea(rectangle);
+            Shape triangle = new Triangle(3, 4, 5);
+            System.out.print("三角形：");
+            ShapeUtil.printArea(triangle);
+        } catch (IllegalArgumentException e) {
+            System.out.println("错误：" + e.getMessage());
+        }
+    }
+}