1 files changed, 44 insertions, 0 deletions
diff --git a/javaparser-core/src/main/java/com/github/javaparser/ast/observer/Observable.java b/javaparser-core/src/main/java/com/github/javaparser/ast/observer/Observable.java
new file mode 100644
index 000000000..ce0f926bf
--- /dev/null
+++ b/javaparser-core/src/main/java/com/github/javaparser/ast/observer/Observable.java
@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2007-2010 Júlio Vilmar Gesser.
+ * Copyright (C) 2011, 2013-2016 The JavaParser Team.
+ *
+ * This file is part of JavaParser.
+ *
+ * JavaParser can be used either under the terms of
+ * a) the GNU Lesser General Public License as published by
+ *     the Free Software Foundation, either version 3 of the License, or
+ *     (at your option) any later version.
+ * b) the terms of the Apache License
+ *
+ * You should have received a copy of both licenses in LICENCE.LGPL and
+ * LICENCE.APACHE. Please refer to those files for details.
+ *
+ * JavaParser 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 Lesser General Public License for more details.
+ */
+
+package com.github.javaparser.ast.observer;
+
+/**
+ * Observable element.
+ */
+public interface Observable {
+
+    /**
+     * Register an observer.
+     */
+    void register(AstObserver observer);
+
+    /**
+     * Unregister an observer. If the given observer was not registered there are no effects.
+     */
+    void unregister(AstObserver observer);
+
+    /**
+     * Was this observer registered?
+     * Note that equals is used to determine if the given observer was registered.
+     */
+    boolean isRegistered(AstObserver observer);
+}