neilotoole 2004/12/10 22:22:58
Modified: collections/src/java/org/apache/commons/collections
ListUtils.java
Log:
Added new methods:
#retainAll(Collection, Collection)
#removeAll(Collection, Collection)
#unmodifiableListCopy(Collection)
Revision Changes Path
1.29 +80 -1
jakarta-commons/collections/src/java/org/apache/commons/collections/ListUtils.java
Index: ListUtils.java
===================================================================
RCS file:
/home/cvs/jakarta-commons/collections/src/java/org/apache/commons/collections/ListUtils.java,v
retrieving revision 1.28
retrieving revision 1.29
diff -u -r1.28 -r1.29
--- ListUtils.java 1 Apr 2004 20:12:00 -0000 1.28
+++ ListUtils.java 11 Dec 2004 06:22:58 -0000 1.29
@@ -258,6 +258,23 @@
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 @@
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;
+ }
+
}
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