diff --git a/Circle.class b/Circle.class
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diff --git a/Rectangle.class b/Rectangle.class
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index 0000000..f45e995
Binary files /dev/null and b/Rectangle.class differ
diff --git a/Shape.class b/Shape.class
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index 0000000..e77741e
Binary files /dev/null and b/Shape.class differ
diff --git a/ShapeTest.class b/ShapeTest.class
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Binary files /dev/null and b/ShapeTest.class differ
diff --git a/ShapeTest.java b/ShapeTest.java
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--- /dev/null
+++ b/ShapeTest.java
@@ -0,0 +1,36 @@
+class Shape {
+    public void draw() {
+        System.out.println("绘制一个图形");
+    }
+}
+
+class Circle extends Shape {
+    @Override
+    public void draw() {
+        System.out.println("绘制一个圆形 ○");
+    }
+}
+
+class Rectangle extends Shape {
+    @Override
+    public void draw() {
+        System.out.println("绘制一个矩形 ▭");
+    }
+}
+
+// 主类必须是 public，名字和文件名完全一致
+public class ShapeTest {
+    public static void drawShape(Shape s) {
+        s.draw();
+    }
+
+    public static void main(String[] args) {
+        Shape circle = new Circle();
+        Shape rectangle = new Rectangle();
+        Shape shape = new Shape();
+
+        drawShape(shape);
+        drawShape(circle);
+        drawShape(rectangle);
+    }
+}
\ No newline at end of file