--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/org.eclipse.core.databinding.observable/src/org/eclipse/core/databinding/observable/list/ListDiffVisitor.d	Tue Apr 21 10:55:51 2009 +0200
@@ -0,0 +1,90 @@
+/*******************************************************************************
+ * Copyright (c) 2007 Matthew Hall and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Matthew Hall - initial API and implementation (bug 208858)
+ ******************************************************************************/
+
+package org.eclipse.core.databinding.observable.list;
+
+import java.util.List;
+
+/**
+ * A visitor for processing differences in a ListDiff.
+ * 
+ * @see ListDiff#acceptcast(ListDiffVisitor)
+ * @since 1.1
+ */
+public abstract class ListDiffVisitor {
+    /**
+     * Notifies the visitor that <code>element</code> was added to the list at
+     * position <code>index</code>.
+     * 
+     * @param index
+     *            the index where the element was added
+     * @param element
+     *            the element that was added
+     */
+    public abstract void handleAdd(int index, Object element);
+
+    /**
+     * Notifies the visitor that <code>element</code> was removed from the
+     * list at position <code>index</code>.
+     * 
+     * @param index
+     *            the index where the element was removed
+     * @param element
+     *            the element that was removed
+     */
+    public abstract void handleRemove(int index, Object element);
+
+    /**
+     * Notifies the visitor that <code>element</code> was moved in the list
+     * from position <code>oldIndex</code> to position <code>newIndex</code>.
+     * <p>
+     * The default implementation of this method calls
+     * {@link #handleRemove(int, Object)} with the old position, then
+     * {@link #handleAdd(int, Object)} with the new position. Clients which are
+     * interested in recognizing "moves" in a list (i.e. calls to
+     * {@link IObservableList#move(int, int)}) should override this method.
+     * 
+     * @param oldIndex
+     *            the index that the element was moved from.
+     * @param newIndex
+     *            the index that the element was moved to.
+     * @param element
+     *            the element that was moved
+     * @see IObservableList#move(int, int)
+     */
+    public void handleMove(int oldIndex, int newIndex, Object element) {
+        handleRemove(oldIndex, element);
+        handleAdd(newIndex, element);
+    }
+
+    /**
+     * Notifies the visitor that <code>oldElement</code>, located at position
+     * <code>index</code> in the list, was replaced by <code>newElement</code>.
+     * <p>
+     * The default implementation of this method calls
+     * {@link #handleRemove(int, Object)} with the old element, then
+     * {@link #handleAdd(int, Object)} with the new element. Clients which are
+     * interested in recognizing "replaces" in a list (i.e. calls to
+     * {@link List#set(int, Object)}) should override this method.
+     * 
+     * @param index
+     *            the index where the element was replaced.
+     * @param oldElement
+     *            the element being replaced.
+     * @param newElement
+     *            the element that replaced oldElement.
+     * @see List#set(int, Object)
+     */
+    public void handleReplace(int index, Object oldElement, Object newElement) {
+        handleRemove(index, oldElement);
+        handleAdd(index, newElement);
+    }
+}