Simple AlertBox in Android

How to show AlertBox in Android:


    protected void alertbox(String title, String mymessage)
    {
    new AlertDialog.Builder(this)
       .setMessage(mymessage).setTitle(title).setCancelable(true)
       .setNeutralButton("OK",new DialogInterface.OnClickListener() {
          public void onClick(DialogInterface dialog, int whichButton){}
          })
       .show();
    }