1 files changed, 75 insertions, 0 deletions
diff --git a/extraplugins/layers/org.eclipse.papyrus.layers.stackmodel/src/org/eclipse/papyrus/layers/stackmodel/util/Collections3.java b/extraplugins/layers/org.eclipse.papyrus.layers.stackmodel/src/org/eclipse/papyrus/layers/stackmodel/util/Collections3.java
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index 00000000000..7d6269fecff
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+++ b/extraplugins/layers/org.eclipse.papyrus.layers.stackmodel/src/org/eclipse/papyrus/layers/stackmodel/util/Collections3.java
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+/*****************************************************************************
+ * Copyright (c) 2013 Cedric Dumoulin.
+ *
+ *    
+ * 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:
+ *  Cedric Dumoulin  Cedric.dumoulin@lifl.fr - Initial API and implementation
+ *
+ *****************************************************************************/
+
+package org.eclipse.papyrus.layers.stackmodel.util;
+
+import java.util.ArrayList;
+import java.util.Collection;
+
+import com.google.common.collect.Collections2;
+
+/**
+ * Set of utility methods for Collections.
+ * @see Collections2
+ * 
+ * @author cedric dumoulin
+ *
+ */
+public class Collections3 {
+
+	/**
+	 * Reset the toChange list to the content of the newContent list.
+	 * Minimize the change calls on the toChange list.
+	 * This method ensure that there is at most 2 writing calls to the list to modify: one 
+	 * removeAll(toBeRemoved) and one addAll(toBeAdded).
+	 * 
+	 * @param toChange
+	 * @param newContent
+	 */
+	public static <E> void resetListTo(Collection<E> toChange, Collection<E> newContent)		{
+
+		// Compute removed and added
+		Collection<E> elementsToRemove = new ArrayList<E>();
+		Collection<E> elementsToAdd = new ArrayList<E>();
+
+		// Compute added and removed elements. Walk both list 2 times. 
+		// This could certainly be improved.
+		// TODO improve the algorithm
+
+		// Compute added elements
+		for( E o : newContent ) {
+			if( !toChange.contains(o)) {
+				elementsToAdd.add(o);
+				continue;
+			}
+		}
+
+		// Compute removed elements
+		for( E o : toChange ) {
+			if( !newContent.contains(o)) {
+				elementsToRemove.add(o);
+				continue;
+			}
+		}
+
+		// Change the list
+		if( ! elementsToRemove.isEmpty()) {
+			toChange.removeAll(elementsToRemove);
+		}
+		if( !elementsToAdd.isEmpty()) {
+			toChange.addAll(elementsToAdd);
+		}
+	}
+
+}