diff --git a/app/src/main/java/org/ntlab/developrx/JavaMainActivity.java b/app/src/main/java/org/ntlab/developrx/JavaMainActivity.java
index efd03d6..a184b71 100644
--- a/app/src/main/java/org/ntlab/developrx/JavaMainActivity.java
+++ b/app/src/main/java/org/ntlab/developrx/JavaMainActivity.java
@@ -15,8 +15,11 @@
         setContentView(R.layout.activity_main_java);
 
         findViewById(R.id.flowable_btn).setOnClickListener(view -> {
-                    rxProcess.flowableReactiveStreams();
-                }
-        );
+            rxProcess.flowableReactiveStreams();
+        });
+
+        findViewById(R.id.observable_btn).setOnClickListener(view -> {
+            rxProcess.observable();
+        });
     }
 }