error: cannot find symbol class RecyclerView

error: cannot find symbol class RecyclerView

git diff
diff --git a/app/build.gradle b/app/build.gradle
index 9e9ddd7..6d6c837 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -25,4 +25,5 @@ dependencies {
     testImplementation 'junit:junit:4.12'
     androidTestImplementation 'com.android.support.test:runner:1.0.2'
     androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
+    implementation 'com.android.support:design:27.0.0+'
 }

-2018-8-2