Added new methods:

#retainAll(Collection, Collection)
#removeAll(Collection, Collection)
#unmodifiableListCopy(Collection)


git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@131824 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/commons/collections/ListUtils.java

@@ -33,7 +33,7 @@ import org.apache.commons.collections.list.UnmodifiableList;
  * Provides utility methods and decorators for {@link List} instances.
  *
  * @since Commons Collections 1.0
- * @version $Revision: 1.28 $ $Date: 2004/04/01 20:12:00 $
+ * @version $Revision: 1.29 $ $Date: 2004/12/11 06:22:58 $
  * 
  * @author Federico Barbieri
  * @author Peter Donald
@@ -258,6 +258,23 @@ public class ListUtils {
         return UnmodifiableList.decorate(list);
     }
 
+    
+	/**
+	 * Returns an unmodifiable list copy of the collection.
+	 * <p>
+	 * This method uses the unmodifiable list implementation in the decorators subpackage.
+	 * @param collection the <code>Collection</code> to copy.
+	 * @return an unmodifiable <code>List</code>.
+	 * @throws IllegalArgumentException if collection is null.
+	 */
+	public static List unmodifiableListCopy(final Collection collection) {
+		if (collection == null) throw new IllegalArgumentException("null not permitted.");
+		
+		final List copy = new ArrayList(collection.size());
+		copy.addAll(collection);
+		return UnmodifiableList.decorate(copy);
+	}
+    
     /**
      * Returns a predicated (validating) list backed by the given list.
      * <p>
@@ -351,4 +368,66 @@ public class ListUtils {
         return FixedSizeList.decorate(list);
     }
 
+    /**
+	 * Returns a List containing all the elements in <code>collection</code>
+	 * that are also in <code>retain</code>. The cardinality of an element <code>e</code>
+	 * in the returned list is the same as the cardinality of <code>e</code>
+	 * in <code>collection</code> unless <code>retain</code> does not contain <code>e</code>, in which
+	 * case the cardinality is zero. This method is useful if you do not wish to modify
+	 * the collection <code>c</code> and thus cannot call <code>collection.retainAll(retain);</code>.
+	 * 
+	 * @param collection the collection whose contents are the target of the #retailAll operation
+	 * @param retain the collection containing the elements to be retained in the returned collection
+	 * @return a <code>List</code> containing all the elements of <code>c</code>
+	 * that occur at least once in <code>retain</code>.
+	 * @throws NullPointerException if either parameter is null
+	 */
+	public static List retainAll(final Collection collection, final Collection retain) {
+		final List list = new ArrayList(Math.min(collection.size(), retain.size()));
+
+		Object item = null;
+		for (final Iterator iter = collection.iterator(); iter.hasNext();)
+		{
+			item = iter.next();
+
+			if (retain.contains(item))
+			{
+				list.add(item);
+			}
+		}
+
+		return list;
+	}
+	
+	/**
+	 * Removes the elements in <code>remove</code> from <code>collection</code>. That is, this
+	 * method returns a list containing all the elements in <code>c</code>
+	 * that are not in <code>remove</code>. The cardinality of an element <code>e</code>
+	 * in the returned collection is the same as the cardinality of <code>e</code>
+	 * in <code>collection</code> unless <code>remove</code> contains <code>e</code>, in which
+	 * case the cardinality is zero. This method is useful if you do not wish to modify
+	 * <code>collection</code> and thus cannot call <code>collection.removeAll(remove);</code>.
+	 * 
+	 * @param collection the collection from which items are removed (in the returned collection)
+	 * @param remove the items to be removed from the returned <code>collection</code>
+	 * @return a <code>List</code> containing all the elements of <code>c</code> except
+	 * any elements that also occur in <code>remove</code>.
+	 * @throws NullPointerException if either parameter is null
+	 */
+	public static List removeAll(final Collection collection, final Collection remove) {
+		final List list = new ArrayList();
+
+		Object o = null;
+		for (final Iterator iter = collection.iterator(); iter.hasNext();)
+		{
+			o = iter.next();
+			if (remove.contains(o) == false)
+			{
+				list.add(o);
+			}
+		}
+
+		return list;
+	}
+    
 }