diff --git a/app/src/main/java/org/ntlab/developrx/JavaMainActivity.java b/app/src/main/java/org/ntlab/developrx/JavaMainActivity.java
index 585d373..cfc7e69 100644
--- a/app/src/main/java/org/ntlab/developrx/JavaMainActivity.java
+++ b/app/src/main/java/org/ntlab/developrx/JavaMainActivity.java
@@ -22,5 +22,6 @@
         findViewById(R.id.interval_btn).setOnClickListener(view -> rxProcess.interval());
         findViewById(R.id.timer_btn).setOnClickListener(view -> rxProcess.timer());
         findViewById(R.id.error_btn).setOnClickListener(view -> rxProcess.error());
+        findViewById(R.id.map_btn).setOnClickListener(view -> rxProcess.map());
     }
 }
diff --git a/app/src/main/java/org/ntlab/developrx/JavaRxProcess.java b/app/src/main/java/org/ntlab/developrx/JavaRxProcess.java
index 5306172..02d8c3e 100644
--- a/app/src/main/java/org/ntlab/developrx/JavaRxProcess.java
+++ b/app/src/main/java/org/ntlab/developrx/JavaRxProcess.java
@@ -173,4 +173,13 @@
     public void error() {
         Flowable.error(new Exception("例外発生")).subscribe(new DebugSubscriber<>());
     }
+
+    /**
+     * データを変換して通知
+     */
+    public void map() {
+        Flowable<String> flowable = Flowable.just("A", "B", "C", "D", "E")
+                .map(data -> data.toLowerCase());
+        flowable.subscribe(new DebugSubscriber<>());
+    }
 }
diff --git a/app/src/main/res/layout/activity_main_java.xml b/app/src/main/res/layout/activity_main_java.xml
index 5a00c5d..29157da 100644
--- a/app/src/main/res/layout/activity_main_java.xml
+++ b/app/src/main/res/layout/activity_main_java.xml
@@ -74,6 +74,14 @@
             app:layout_constraintStart_toStartOf="parent"
             app:layout_constraintTop_toBottomOf="@id/timer_btn" />
 
+        <Button
+            android:id="@+id/map_btn"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="map"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toBottomOf="@id/error_btn" />
+
     </android.support.constraint.ConstraintLayout>
 
 </ScrollView>