diff --git a/w5/Shape.java b/w5/Shape.java
new file mode 100644
index 0000000..cebef67
--- /dev/null
+++ b/w5/Shape.java
@@ -0,0 +1,151 @@
+package com.example.shape;
+
+public abstract class Shape {
+    public abstract double getArea();
+}
+
+class Circle extends Shape {
+    private double radius;
+    private static final double PI = 3.1415926;
+    
+    public Circle(double radius) {
+        if (radius <= 0) {
+            throw new IllegalArgumentException("半径必须大于0");
+        }
+        this.radius = radius;
+    }
+    
+    @Override
+    public double getArea() {
+        return PI * radius * radius;
+    }
+    
+    public double getRadius() {
+        return radius;
+    }
+    
+    public void setRadius(double radius) {
+        if (radius <= 0) {
+            throw new IllegalArgumentException("半径必须大于0");
+        }
+        this.radius = radius;
+    }
+}
+
+class Rectangle extends Shape {
+    private double length;
+    private double width;
+    
+    public Rectangle(double length, double width) {
+        if (length <= 0 || width <= 0) {
+            throw new IllegalArgumentException("长和宽必须大于0");
+        }
+        this.length = length;
+        this.width = width;
+    }
+    
+    @Override
+    public double getArea() {
+        return length * width;
+    }
+    
+    public double getLength() {
+        return length;
+    }
+    
+    public void setLength(double length) {
+        if (length <= 0) {
+            throw new IllegalArgumentException("长必须大于0");
+        }
+        this.length = length;
+    }
+    
+    public double getWidth() {
+        return width;
+    }
+    
+    public void setWidth(double width) {
+        if (width <= 0) {
+            throw new IllegalArgumentException("宽必须大于0");
+        }
+        this.width = width;
+    }
+}
+
+class Triangle extends Shape {
+    private double a;
+    private double b;
+    private double c;
+    
+    public Triangle(double a, double b, double c) {
+        // 校验三边>0，且满足三角形三边关系（任意两边之和>第三边）
+        if (a <= 0 || b <= 0 || c <= 0) {
+            throw new IllegalArgumentException("边长必须大于0");
+        }
+        if (a + b <= c || a + c <= b || b + c <= a) {
+            throw new IllegalArgumentException("不满足三角形三边关系，无法构成三角形");
+        }
+        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));
+    }
+    
+    public double getA() {
+        return a;
+    }
+    
+    public void setA(double a) {
+        if (a <= 0) {
+            throw new IllegalArgumentException("边长必须大于0");
+        }
+        this.a = a;
+        if (a + b <= c || a + c <= b || b + c <= a) {
+            throw new IllegalArgumentException("不满足三角形三边关系，无法构成三角形");
+        }
+    }
+    
+    public double getB() {
+        return b;
+    }
+    
+    public void setB(double b) {
+        if (b <= 0) {
+            throw new IllegalArgumentException("边长必须大于0");
+        }
+        this.b = b;
+        if (a + b <= c || a + c <= b || b + c <= a) {
+            throw new IllegalArgumentException("不满足三角形三边关系，无法构成三角形");
+        }
+    }
+    
+    public double getC() {
+        return c;
+    }
+    
+    public void setC(double c) {
+        if (c <= 0) {
+            throw new IllegalArgumentException("边长必须大于0");
+        }
+        this.c = c;
+        if (a + b <= c || a + c <= b || b + c <= a) {
+            throw new IllegalArgumentException("不满足三角形三边关系，无法构成三角形");
+        }
+    }
+}
+
+class ShapeUtil {
+    public static void printArea(Shape shape) {
+        if (shape == null) {
+            System.out.println("图形对象不能为空！");
+            return;
+        }
+        double area = shape.getArea();
+        System.out.printf("该图形的面积为：%.2f%n", area);
+    }
+}
\ No newline at end of file
diff --git a/w5/desktop.ini b/w5/desktop.ini
new file mode 100644
index 0000000..71f71dd
--- /dev/null
+++ b/w5/desktop.ini
@@ -0,0 +1,2 @@
+[LocalizedFileNames]
+Shape.java=@Shape.java,0
diff --git a/w5/反思.txt b/w5/反思.txt
new file mode 100644
index 0000000..91fc695
--- /dev/null
+++ b/w5/反思.txt
@@ -0,0 +1,3 @@
+1.本次重构通过抽象类+继承实现了代码的统一管理，解决了原独立类无法统一处理的问题，体现了面向对象多态的优势
+2.代码中增加了参数校验，避免了非法数据导致的计算错误，提升了健壮性
+3.工具类 ShapeUtil 通过多态实现了开闭原则：新增图形类（如正方形）无需修改工具类，只需新增 Shape 子类即可，符合面向对象设计原则。
\ No newline at end of file
diff --git a/w5/实验报告.txt b/w5/实验报告.txt
new file mode 100644
index 0000000..24146da
--- /dev/null
+++ b/w5/实验报告.txt
@@ -0,0 +1,8 @@
+AI使用情况：
+1.通过AI辅助更深刻地理解了抽象类，继承和多态的概念，以及Circle,Rectangle,Triangle三个子类如何继承并实现getArea方法
+2.用AI梳理了类的结构和UML类图的含义，知道我正确使用了@override方法
+3.利用AI检查程序漏洞，润色代码
+
+组合VS继承问题：
+继承是一种“is-a”的关系，具有高耦合度，编译期确定继承关系，灵活性较差，适用于类之间存在明确的父子关系。
+组合是一种“has-a”的关系，耦合度低，但运行期可动态替换组合对象，灵活性高，适用于从属关系
\ No newline at end of file
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