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diff --git a/javaparser-core/src/main/java/com/github/javaparser/ast/DataKey.java b/javaparser-core/src/main/java/com/github/javaparser/ast/DataKey.java
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+/*
+ * 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;
+
+/**
+ * A key to a piece of data associated with a {@link Node} at runtime.
+ * The key contains type information that can be used to check the
+ * type of any user data value for the key when the value is set. DataKey is abstract in order to
+ * force the creation of a subtype. That subtype is used to test for identity when looking for the
+ * user data because actual object identity would suffer from problems under serialization.
+ * So, the correct way to declare a DataKey is like this:
+ * <p>
+ * <pre>
+ * <code>
+ * public static final DataKey&lt;Role&gt; ROLE = new DataKey&lt;Role&gt;() { };
+ * </code>
+ * </pre>
+ * <p>
+ * This code was taken from the <a href="http://wicket.apache.org/">Wicket project</a>.
+ *
+ * @param <T> The type of the object which is stored
+ * @see Node#getData(DataKey)
+ */
+public abstract class DataKey<T> {
+    @Override
+    public int hashCode() {
+        return getClass().hashCode();
+    }
+
+    /**
+     * @see java.lang.Object#equals(java.lang.Object)
+     */
+    @Override
+    public boolean equals(Object obj) {
+        return obj != null && getClass().equals(obj.getClass());
+    }
+}