Adicionei um botão

app/src/main/java/com/example/git_teste/MainActivity.java

@@ -20,5 +20,6 @@ public class MainActivity extends AppCompatActivity {
             v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);
             return insets;
         });
+        // Hello World button
     }
 }