diff --git a/chapter6/haesa/refactor-chapter6-1.java b/chapter6/haesa/refactor-chapter6-1.java
new file mode 100644
index 0000000..e44a420
--- /dev/null
+++ b/chapter6/haesa/refactor-chapter6-1.java
@@ -0,0 +1,12 @@
+// What is the difference between the following codes?
+
+// 가솔린 차만 사용 가능하다는 제약이 있음
+public interface Vehicle {
+    double getFuelTankCapacityInGallons();
+    double getGallonsOfGasoline();
+}
+
+// 연료 종류에 상관 없이 사용 가능
+public interface Vehicle {
+    double getPercentFuelRemaining();
+}
\ No newline at end of file