Eccomi,

l'applicazione quando viene lanciata crasha dando come messaggio: "Sorry! The application ProvaDatabase (process com.example.provadatabase) has stopped unexpectedly. Please try again"

LogCat:
codice:
06-27 10:15:36.626: D/AndroidRuntime(427): Shutting down VM 
06-27 10:15:36.676: W/dalvikvm(427): threadid=1: thread exiting with uncaught exception (group=0x4001d800) 
06-27 10:15:36.736: E/AndroidRuntime(427): FATAL EXCEPTION: main 
06-27 10:15:36.736: E/AndroidRuntime(427): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.provadatabase/com.example.provadatabase.MainActivity}: java.lang.ClassCastException: com.example.provadatabase.MainActivity 
06-27 10:15:36.736: E/AndroidRuntime(427): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585) 
06-27 10:15:36.736: E/AndroidRuntime(427): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
06-27 10:15:36.736: E/AndroidRuntime(427): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
06-27 10:15:36.736: E/AndroidRuntime(427): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
06-27 10:15:36.736: E/AndroidRuntime(427): at android.os.Handler.dispatchMessage(Handler.java:99) 
06-27 10:15:36.736: E/AndroidRuntime(427): at android.os.Looper.loop(Looper.java:123) 06-27 10:15:36.736: E/AndroidRuntime(427): at android.app.ActivityThread.main(ActivityThread.java:4627) 
06-27 10:15:36.736: E/AndroidRuntime(427): at java.lang.reflect.Method.invokeNative(Native Method) 
06-27 10:15:36.736: E/AndroidRuntime(427): at java.lang.reflect.Method.invoke(Method.java:521) 
06-27 10:15:36.736: E/AndroidRuntime(427): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
06-27 10:15:36.736: E/AndroidRuntime(427): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
06-27 10:15:36.736: E/AndroidRuntime(427): at dalvik.system.NativeStart.main(Native Method) 
06-27 10:15:36.736: E/AndroidRuntime(427): Caused by: java.lang.ClassCastException: com.example.provadatabase.MainActivity 
06-27 10:15:36.736: E/AndroidRuntime(427): at android.app.Instrumentation.newActivity(Instrumentation.java:1021) 
06-27 10:15:36.736: E/AndroidRuntime(427): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577) 
06-27 10:15:36.736: E/AndroidRuntime(427): ... 11 more
Ps. ho modificato così
codice:
while (res.next()) { 
System.out.println(res.getString(1)); 
}