Add query interface.

diff --git a/src/main/java/net/pterodactylus/reactor/Query.java b/src/main/java/net/pterodactylus/reactor/Query.java
new file mode 100644 (file)
index 0000000..0b46a39
--- /dev/null
+++ b/src/main/java/net/pterodactylus/reactor/Query.java
@@ -0,0 +1,35 @@
+/*
+ * Reactor - Query.java - Copyright © 2013 David Roden
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package net.pterodactylus.reactor;
+
+/**
+ * A query is used to retrieve the current {@link State} of a system.
+ *
+ * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+ */
+public interface Query {
+
+       /**
+        * Retrieves the current state of the system. The returned state is never
+        * {@code null}.
+        *
+        * @return The current state of the system.
+        */
+       public State state();
+
+}