Author: mbenson
Date: Fri Sep 11 17:48:55 2009
New Revision: 813951
URL: http://svn.apache.org/viewvc?rev=813951&view=rev
Log:
[COLLECTIONS-286] CollectionsUtils.extractSingleton
Modified:
commons/proper/collections/branches/collections_jdk5_branch/src/java/org/apache/commons/collections/CollectionUtils.java
commons/proper/collections/branches/collections_jdk5_branch/src/test/org/apache/commons/collections/TestCollectionUtils.java
Modified:
commons/proper/collections/branches/collections_jdk5_branch/src/java/org/apache/commons/collections/CollectionUtils.java
URL:
http://svn.apache.org/viewvc/commons/proper/collections/branches/collections_jdk5_branch/src/java/org/apache/commons/collections/CollectionUtils.java?rev=813951&r1=813950&r2=813951&view=diff
==============================================================================
---
commons/proper/collections/branches/collections_jdk5_branch/src/java/org/apache/commons/collections/CollectionUtils.java
(original)
+++
commons/proper/collections/branches/collections_jdk5_branch/src/java/org/apache/commons/collections/CollectionUtils.java
Fri Sep 11 17:48:55 2009
@@ -1291,4 +1291,17 @@
return TransformedCollection.decorate(collection, transformer);
}
+ /**
+ * Extract the lone element of the specified Collection.
+ * @param <E> collection type
+ * @param collection to read
+ * @return sole member of collection
+ * @throws IllegalArgumentException if collection is null/empty or
contains more than one element
+ */
+ public static <E> E extractSingleton(Collection<E> collection) {
+ if (collection == null || collection.size() != 1) {
+ throw new IllegalArgumentException("Can extract singleton only
when collection size == 1");
+ }
+ return collection.iterator().next();
+ }
}
Modified:
commons/proper/collections/branches/collections_jdk5_branch/src/test/org/apache/commons/collections/TestCollectionUtils.java
URL:
http://svn.apache.org/viewvc/commons/proper/collections/branches/collections_jdk5_branch/src/test/org/apache/commons/collections/TestCollectionUtils.java?rev=813951&r1=813950&r2=813951&view=diff
==============================================================================
---
commons/proper/collections/branches/collections_jdk5_branch/src/test/org/apache/commons/collections/TestCollectionUtils.java
(original)
+++
commons/proper/collections/branches/collections_jdk5_branch/src/test/org/apache/commons/collections/TestCollectionUtils.java
Fri Sep 11 17:48:55 2009
@@ -1414,6 +1414,29 @@
assertEquals(collectionA, Arrays.asList(a));
}
+ @Test
+ public void extractSingleton() {
+ ArrayList<String> coll = null;
+ try {
+ CollectionUtils.extractSingleton(coll);
+ fail("expected IllegalArgumentException from
extractSingleton(null)");
+ } catch (IllegalArgumentException e) {
+ }
+ coll = new ArrayList<String>();
+ try {
+ CollectionUtils.extractSingleton(coll);
+ fail("expected IllegalArgumentException from
extractSingleton(empty)");
+ } catch (IllegalArgumentException e) {
+ }
+ coll.add("foo");
+ assertEquals("foo", CollectionUtils.extractSingleton(coll));
+ coll.add("bar");
+ try {
+ CollectionUtils.extractSingleton(coll);
+ fail("expected IllegalArgumentException from extractSingleton(size
== 2)");
+ } catch (IllegalArgumentException e) {
+ }
+ }
/**
* Records the next object returned for a mock iterator
