Why is this code doesent work on android 8.1.0

Why is this code doesn’t work on android 8.1.0?, i already used the else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) statement. Is it because it should change KITKAT to LOLLIPOP?

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P){
activity.getWindow().addFlags(WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS);
WindowManager.LayoutParams params = activity.getWindow().getAttributes();
params.layoutInDisplayCutoutMode = WindowManager.LayoutParams.LAYOUT_IN_DISPLAY_CUTOUT_MODE_SHORT_EDGES;
activity.getWindow().setAttributes(params);

activity.getWindow().getDecorView().setSystemUiVisibility(
View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN |
View.SYSTEM_UI_FLAG_LAYOUT_STABLE |
View.SYSTEM_UI_FLAG_FULLSCREEN |
View.SYSTEM_UI_FLAG_HIDE_NAVIGATION 
View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY);
} else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT){
activity.getWindow().getDecorView().setSystemUiVisibility(
View.SYSTEM_UI_FLAG_FULLSCREEN |
View.SYSTEM_UI_FLAG_HIDE_NAVIGATION |
View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY);
}