move files from src/main/java to src/main/kotlin, no functionality change

app/build.gradle

@@ -28,6 +28,10 @@ android {
         }
     }
 
+    sourceSets {
+        main.java.srcDirs += 'src/main/kotlin'
+    }
+
     lintOptions {
         checkReleaseBuilds false
         abortOnError false