cannot disable prev scroll

how to disable prevscroll if the image in position 0 ??? , i have make this.
@Override
public void onPageSelected(int position) {
if (position == file_maps.size() - 1) {
masuk.setVisibility(View.VISIBLE);
} else {
masuk.setVisibility(View.GONE);
}
if (previousPosition == file_maps.size() - 1 && position == 0) {
imageslider.movePrevPosition(false);
return;
} else if (previousPosition == 0 && position == file_maps.size() - 1) {
imageslider.moveNextPosition(false);
return;
}
previousPosition = position;
}

but the prev scrool cannot disable, just scrol to position 4, but back to position 0 again, NOT DISABLE.