2 * Rhynodge - FileExistenceTrigger.java - Copyright © 2013 David Roden
4 * This program is free software: you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation, either version 3 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program. If not, see <http://www.gnu.org/licenses/>.
18 package net.pterodactylus.rhynodge.triggers;
20 import net.pterodactylus.rhynodge.Reaction;
21 import net.pterodactylus.rhynodge.State;
22 import net.pterodactylus.rhynodge.Trigger;
23 import net.pterodactylus.rhynodge.output.DefaultOutput;
24 import net.pterodactylus.rhynodge.output.Output;
25 import net.pterodactylus.rhynodge.states.FileState;
27 import com.google.common.base.Preconditions;
30 * A trigger that detects changes in the existence of a file.
32 * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
34 public class FileExistenceTrigger implements Trigger {
36 /** Whether a change is triggered. */
37 private boolean triggered;
47 public State mergeStates(State previousState, State currentState) {
48 Preconditions.checkState(previousState instanceof FileState, "previousState is not a FileState");
49 Preconditions.checkState(currentState instanceof FileState, "currentState is not a FileState");
50 triggered = ((FileState) previousState).exists() != ((FileState) currentState).exists();
58 public boolean triggers() {