diff --git a/w4/Circle.java b/w4/Circle.java
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--- /dev/null
+++ b/w4/Circle.java
@@ -0,0 +1,35 @@
+/**
+  * 圆形类，继承Shape，实现面积计算
+  */
+ public class Circle extends Shape {
+     // 圆的半径
+     private double radius;
+     // π常量
+     private static final double PI = 3.1415926;
+     /**
+      * 无参构造
+      */
+     public Circle() {}
+     /**
+      * 带参构造，初始化半径
+      * @param radius 半径
+      */
+     public Circle(double radius) {
+         this.radius = radius;
+     }
+     /**
+      * 实现父类抽象方法，计算圆面积：πr²
+      * @return 圆的面积
+      */
+     @Override
+     public double getArea() {
+         return PI * radius * radius;
+     }
+     // Getter和Setter
+     public double getRadius() {
+         return radius;
+     }
+     public void setRadius(double radius) {
+         this.radius = radius;
+     }
+ }
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diff --git a/w4/Main.java b/w4/Main.java
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+++ b/w4/Main.java
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+/**
+  * 测试类，验证图形面积计算器的功能
+  */
+ public class Main {
+     public static void main(String[] args) {
+         // 1. 创建圆形对象（半径5）
+         Shape circle = new Circle(5);
+         // 2. 创建矩形对象（长4，宽3）
+         Shape rectangle = new Rectangle(4, 3);
+         // 3. 创建三角形对象（底6，高4）
+         Shape triangle = new Triangle(6, 4);
+         // 4. 通过工具类统一打印面积（多态效果）
+         System.out.println("=== 圆形面积 ===");
+         ShapeUtil.printArea(circle);
+         System.out.println("\n=== 矩形面积 ===");
+         ShapeUtil.printArea(rectangle);
+         System.out.println("\n=== 三角形面积 ===");
+         ShapeUtil.printArea(triangle);
+     }
+ }
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diff --git a/w4/README.md b/w4/README.md
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--- /dev/null
+++ b/w4/README.md
@@ -0,0 +1,30 @@
+图形面积计算器重构实验
+
+一、实验背景
+
+现有Circle、Rectangle、Triangle三个图形类独立存在，无法统一处理。本实验通过抽象类+继承重构，实现图形面积的统一计算与打印。
+
+
+
+二、文件说明
+
+Shape.java：抽象父类，定义面积计算接口
+
+Circle.java：圆形类，继承Shape
+
+Rectangle.java：矩形类，继承Shape
+
+Triangle.java：三角形类，继承Shape
+
+ShapeUtil.java：工具类，统一打印面积
+
+Main.java：测试类，程序入口
+
+
+
+三、运行步骤
+
+编译：javac \*.java
+
+运行：java Main
+
diff --git a/w4/Rectangle.java b/w4/Rectangle.java
new file mode 100644
index 0000000..7437bc0
--- /dev/null
+++ b/w4/Rectangle.java
@@ -0,0 +1,43 @@
+/**
+  * 矩形类，继承Shape，实现面积计算
+  */
+ public class Rectangle extends Shape {
+     // 长
+     private double length;
+     // 宽
+     private double width;
+     /**
+      * 无参构造
+      */
+     public Rectangle() {}
+     /**
+      * 带参构造，初始化长和宽
+      * @param length 长
+      * @param width 宽
+      */
+     public Rectangle(double length, double width) {
+         this.length = length;
+         this.width = width;
+     }
+     /**
+      * 实现父类抽象方法，计算矩形面积：长×宽
+      * @return 矩形的面积
+      */
+     @Override
+     public double getArea() {
+         return length * width;
+     }
+     // Getter和Setter
+     public double getLength() {
+         return length;
+     }
+     public void setLength(double length) {
+         this.length = length;
+     }
+     public double getWidth() {
+         return width;
+     }
+     public void setWidth(double width) {
+         this.width = width;
+     }
+ }
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diff --git a/w4/Shape.java b/w4/Shape.java
new file mode 100644
index 0000000..2c268c6
--- /dev/null
+++ b/w4/Shape.java
@@ -0,0 +1,10 @@
+/**
+ * 图形抽象父类，定义统一的面积计算接口
+ */
+public abstract class Shape {
+    /**
+     * 抽象方法：计算图形面积，由子类具体实现
+     * @return 图形面积
+     */
+    public abstract double getArea();
+}
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diff --git a/w4/ShapeUtil.java b/w4/ShapeUtil.java
new file mode 100644
index 0000000..080928f
--- /dev/null
+++ b/w4/ShapeUtil.java
@@ -0,0 +1,12 @@
+/**
+ * 图形工具类，提供统一的面积打印方法
+ */
+public class ShapeUtil {
+    /**
+     * 统一打印图形面积的方法，支持所有Shape子类
+     * @param shape 图形对象（Circle/Rectangle/Triangle）
+     */
+    public static void printArea(Shape shape) {
+        System.out.println("该图形的面积为：" + shape.getArea());
+    }
+}
\ No newline at end of file
diff --git a/w4/Triangle.java b/w4/Triangle.java
new file mode 100644
index 0000000..0489a3a
--- /dev/null
+++ b/w4/Triangle.java
@@ -0,0 +1,43 @@
+/**
+  * 三角形类，继承Shape，实现面积计算
+  */
+ public class Triangle extends Shape {
+     // 底
+     private double base;
+     // 高
+     private double height;
+     /**
+      * 无参构造
+      */
+     public Triangle() {}
+     /**
+      * 带参构造，初始化底和高
+      * @param base 底
+      * @param height 高
+      */
+     public Triangle(double base, double height) {
+         this.base = base;
+         this.height = height;
+     }
+     /**
+      * 实现父类抽象方法，计算三角形面积：底×高/2
+      * @return 三角形的面积
+      */
+     @Override
+     public double getArea() {
+         return base * height / 2;
+     }
+     // Getter和Setter
+     public double getBase() {
+         return base;
+     }
+     public void setBase(double base) {
+         this.base = base;
+     }
+     public double getHeight() {
+         return height;
+     }
+     public void setHeight(double height) {
+         this.height = height;
+     }
+ }
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