diff --git a/03：类与对象/04.md b/03：类与对象/04.md
index 7c446e0..8c06748 100644
--- a/03：类与对象/04.md
+++ b/03：类与对象/04.md
@@ -492,11 +492,13 @@ public class TestEdible {
 	public static void main(String[] args) {
 		Object[] objects = { new Tiger(), new Chicken(), new Apple() };
 		for (int i = 0; i < objects.length; i++) {
-			if (objects[i] instanceof Edible)
-				System.out.println(((Edible) objects[i]).howToEat());
-
+			if (objects[i] instanceof Edible) {
+				Edible e = (Edible) objects[i];
+				System.out.println(e.howToEat());
+			}
 			if (objects[i] instanceof Animal) {
-				System.out.println(((Animal) objects[i]).sound());
+				Animal a = (Animal) objects[i];
+				System.out.println(a.sound());
 			}
 		}
 	}