This will force-stop all applications including system-app

    try
     {
        Process suProcess = Runtime.getRuntime().exec("su");
        DataOutputStream os = new DataOutputStream(suProcess.getOutputStream());

        os.writeBytes("adb shell" + "\n");
        os.flush();

        Context newContext=this;
        ActivityManager activityManager = (ActivityManager) newContext.getSystemService( Context.ACTIVITY_SERVICE );
        List<RunningAppProcessInfo> appProcesses = activityManager.getRunningAppProcesses();
        for(RunningAppProcessInfo appProcess : appProcesses){
            if(appProcess.processName.equals("com.yourPackageName")){
             }
             else{
                os.writeBytes("am force-stop "+appProcess.processName + "\n");
             }
          }

        os.flush();
        os.close();
        suProcess.waitFor();

     }

     catch (IOException ex)
     {
         ex.getMessage();
         Toast.makeText(getApplicationContext(), ex.getMessage(),Toast.LENGTH_LONG).show();
     }
     catch (SecurityException ex)
     {
         Toast.makeText(getApplicationContext(), "Can't get root access2",
                   Toast.LENGTH_LONG).show();
     }
     catch (Exception ex)
     {
         Toast.makeText(getApplicationContext(), "Can't get root access3",
                   Toast.LENGTH_LONG).show();
     }