diff --git a/w4/Circle.java b/w4/Circle.java
new file mode 100644
index 0000000..3f6c351
--- /dev/null
+++ b/w4/Circle.java
@@ -0,0 +1,25 @@
+// 圆形类，继承抽象类Shape
+public class Circle extends Shape {
+    // 半径
+    private double radius;
+
+    // 构造方法：初始化半径
+    public Circle(double radius) {
+        this.radius = radius;
+    }
+
+    // 重写getArea方法：圆的面积 = π * r²
+    @Override
+    public double getArea() {
+        return Math.PI * radius * radius;
+    }
+
+    // 可选：getter/setter方法（方便后续扩展）
+    public double getRadius() {
+        return radius;
+    }
+
+    public void setRadius(double radius) {
+        this.radius = radius;
+    }
+}
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diff --git a/w4/Rectangle.java b/w4/Rectangle.java
new file mode 100644
index 0000000..6b7b842
--- /dev/null
+++ b/w4/Rectangle.java
@@ -0,0 +1,35 @@
+// 矩形类，继承抽象类Shape
+public class Rectangle extends Shape {
+    // 长、宽
+    private double length;
+    private double width;
+
+    // 构造方法：初始化长和宽
+    public Rectangle(double length, double width) {
+        this.length = length;
+        this.width = width;
+    }
+
+    // 重写getArea方法：矩形面积 = 长 * 宽
+    @Override
+    public double getArea() {
+        return length * width;
+    }
+
+    // 可选：getter/setter方法
+    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;
+    }
+}
\ No newline at end of file
diff --git a/w4/Shape.java b/w4/Shape.java
new file mode 100644
index 0000000..3fb2f5c
--- /dev/null
+++ b/w4/Shape.java
@@ -0,0 +1,5 @@
+// 抽象父类 Shape，定义所有图形的统一行为
+public abstract class Shape {
+    // 抽象方法：计算面积，由子类具体实现
+    public abstract double getArea();
+}
\ No newline at end of file
diff --git a/w4/ShapeUtil.java b/w4/ShapeUtil.java
new file mode 100644
index 0000000..43f07e0
--- /dev/null
+++ b/w4/ShapeUtil.java
@@ -0,0 +1,22 @@
+// 工具类：提供统一处理图形的方法
+public class ShapeUtil {
+    // 统一打印面积的方法：接收任意Shape子类对象
+    public static void printArea(Shape shape) {
+        System.out.println("图形面积为：" + shape.getArea());
+    }
+
+    // 测试主方法（可直接运行验证）
+    public static void main(String[] args) {
+        // 测试圆形：半径5
+        Shape circle = new Circle(5);
+        printArea(circle); // 输出约78.54
+
+        // 测试矩形：长4，宽3
+        Shape rectangle = new Rectangle(4, 3);
+        printArea(rectangle); // 输出12.0
+
+        // 测试三角形：底6，高4
+        Shape triangle = new Triangle(6, 4);
+        printArea(triangle); // 输出12.0
+    }
+}
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diff --git a/w4/Triangle.java b/w4/Triangle.java
new file mode 100644
index 0000000..17ba5c2
--- /dev/null
+++ b/w4/Triangle.java
@@ -0,0 +1,35 @@
+// 三角形类，继承抽象类Shape
+public class Triangle extends Shape {
+    // 底、高
+    private double base;
+    private double height;
+
+    // 构造方法：初始化底和高
+    public Triangle(double base, double height) {
+        this.base = base;
+        this.height = height;
+    }
+
+    // 重写getArea方法：三角形面积 = 底 * 高 / 2
+    @Override
+    public double getArea() {
+        return base * height / 2;
+    }
+
+    // 可选：getter/setter方法
+    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;
+    }
+}
\ No newline at end of file