diff --git a/W4/ShiYan.java b/W4/ShiYan.java
new file mode 100644
index 0000000..f017a27
--- /dev/null
+++ b/W4/ShiYan.java
@@ -0,0 +1,55 @@
+package com.rental;
+public class ShiYan {
+    static abstract class Shape {
+        public abstract double getArea();
+    }
+    static class Circle extends Shape {
+        private double radius;
+
+        public Circle(double radius) {
+            this.radius = radius;
+        }
+        @Override
+        public double getArea() {
+            return Math.PI * radius * radius;
+        }
+    }
+    // 矩形
+    static 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;
+        }
+    }
+    static class Triangle extends Shape {
+        private double base;
+        private double height;
+        public Triangle(double base, double height) {
+            this.base = base;
+            this.height = height;
+        }
+        @Override
+        public double getArea() {
+            return 0.5 * base * height;
+        }
+    }
+    static class ShapeUtil {
+        public static void printArea(Shape shape) {
+            System.out.println("图形面积为：" + shape.getArea());
+        }
+    }
+    public static void main(String[] args) {
+        Shape circle = new Circle(5);
+        Shape rectangle = new Rectangle(4, 6);
+        Shape triangle = new Triangle(3, 8);
+        ShapeUtil.printArea(circle);
+        ShapeUtil.printArea(rectangle);
+        ShapeUtil.printArea(triangle);
+    }
+}
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