You're using 0 (zero) instead of i inside your loop.
for (int i = 0; i < activityes.size(); i++){
Log.e("APP: "+i, activityes.get(i).processName);
if (!activityes.get(i).processName.equals("app.android.myapp")){
Process.killProcess(activityes.get(i).pid);
}
}