java.lang.classnotfoundexception didn't find class on path dexpathlist

Got the following Error:

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.android.geofence/com.example.android.geofence.MainActivity}: java.lang.ClassNotFoundException: Didn't find class "com.example.android.geofence.MainActivity" on path: DexPathList[[zip file "/system/framework/com.google.android.maps.jar", zip file "/data/app/com.example.android.geofence-5.apk"],nativeLibraryDirectories=[/data/app-lib/com.example.android.geofence-5, /vendor/lib, /system/lib]]

solution:

1. Right click on your project and select Properties.
2. Select Java Build Path from the menu on the left.
3. Select the Order and Export tab.
4. From the list make sure the libraries or external jars you added to your project are checked.
5. Finally, clean your project & run.