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[COLLECTIONS-421] Cleanup of ListUtils, use wildcards for hashCodeForList, use generic example in javadoc, thanks to Benedikt Ritter. 

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/collections/trunk@1361590 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Thomas Neidhart 2012-07-14 21:36:25 +00:00
parent 37ace6950e
commit 20fdf174fe
1 changed files with 23 additions and 18 deletions
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41
src/main/java/org/apache/commons/collections/ListUtils.java
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@ -35,15 +35,7 @@ import org.apache.commons.collections.list.UnmodifiableList;
* Provides utility methods and decorators for {@link List} instances.
*
* @since Commons Collections 1.0
* @version $Revision$
*
* @author Federico Barbieri
* @author Peter Donald
* @author Paul Jack
* @author Stephen Colebourne
* @author Neil O'Toole
* @author Matthew Hawthorne
* @author Dave Meikle
* @version $Id$
*/
public class ListUtils {
@ -65,6 +57,7 @@ public class ListUtils {
* Returns a new list containing all elements that are contained in
* both given lists.
*
* @param <E> the element type
* @param list1 the first list
* @param list2 the second list
* @return the intersection of those two lists
@ -101,6 +94,7 @@ public class ListUtils {
* contains one occurrence, then the returned list will still contain
* one occurrence.
*
* @param <E> the element type
* @param list1 the list to subtract from
* @param list2 the list to subtract
* @return a new list containing the results
@ -121,6 +115,7 @@ public class ListUtils {
* Returns the sum of the given lists. This is their intersection
* subtracted from their union.
*
* @param <E> the element type
* @param list1 the first list
* @param list2 the second list
* @return a new list containing the sum of those lists
@ -135,6 +130,7 @@ public class ListUtils {
* first list. The {@link List#addAll(Collection)} operation is
* used to append the two given lists into a new list.
*
* @param <E> the element type
* @param list1 the first list
* @param list2 the second list
* @return a new list containing the union of those lists
@ -212,15 +208,15 @@ public class ListUtils {
* @param list the list to generate the hashCode for, may be null
* @return the hash code
*/
public static <E> int hashCodeForList(final Collection<E> list) {
public static int hashCodeForList(final Collection<?> list) {
if (list == null) {
return 0;
}
int hashCode = 1;
Iterator<E> it = list.iterator();
Iterator<?> it = list.iterator();
while (it.hasNext()) {
E obj = it.next();
Object obj = it.next();
hashCode = 31 * hashCode + (obj == null ? 0 : obj.hashCode());
}
return hashCode;
@ -235,6 +231,7 @@ public class ListUtils {
* 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 <E> the element type
* @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>
@ -262,6 +259,7 @@ public class ListUtils {
* 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 <E> the element type
* @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
@ -298,6 +296,7 @@ public class ListUtils {
*
* This method uses the implementation in the decorators subpackage.
*
* @param <E> the element type
* @param list the list to synchronize, must not be null
* @return a synchronized list backed by the given list
* @throws IllegalArgumentException if the list is null
@ -311,6 +310,7 @@ public class ListUtils {
* <p>
* This method uses the implementation in the decorators subpackage.
*
* @param <E> the element type
* @param list the list to make unmodifiable, must not be null
* @return an unmodifiable list backed by the given list
* @throws IllegalArgumentException if the list is null
@ -327,6 +327,7 @@ public class ListUtils {
* It is important not to use the original list after invoking this method,
* as it is a backdoor for adding invalid objects.
*
* @param <E> the element type
* @param list the list to predicate, must not be null
* @param predicate the predicate for the list, must not be null
* @return a predicated list backed by the given list
@ -350,6 +351,7 @@ public class ListUtils {
* Existing entries in the specified list will not be transformed.
* If you want that behaviour, see {@link TransformedList#transformedList}.
*
* @param <E> the element type
* @param list the list to predicate, must not be null
* @param transformer the transformer for the list, must not be null
* @return a transformed list backed by the given list
@ -369,20 +371,21 @@ public class ListUtils {
* For instance:
*
* <pre>
* Factory factory = new Factory() {
* public Object create() {
* Factory&lt;Date&gt; factory = new Factory&lt;Date&gt;() {
* public Date create() {
* return new Date();
* }
* }
* List lazy = ListUtils.lazyList(new ArrayList(), factory);
* Object obj = lazy.get(3);
* List&lt;Date&gt; lazy = ListUtils.lazyList(new ArrayList&lt;Date&gt;(), factory);
* Date date = lazy.get(3);
* </pre>
*
* After the above code is executed, <code>obj</code> will contain
* After the above code is executed, <code>date</code> will contain
* a new <code>Date</code> instance. Furthermore, that <code>Date</code>
* instance is the fourth element in the list. The first, second,
* and third element are all set to <code>null</code>.
*
* @param <E> the element type
* @param list the list to make lazy, must not be null
* @param factory the factory for creating new objects, must not be null
* @return a lazy list backed by the given list
@ -396,8 +399,9 @@ public class ListUtils {
* Returns a fixed-sized list backed by the given list.
* Elements may not be added or removed from the returned list, but
* existing elements can be changed (for instance, via the
* {@link List#set(int,Object)} method).
* {@link List#set(int,E)} method).
*
* @param <E> the element type
* @param list the list whose size to fix, must not be null
* @return a fixed-size list backed by that list
* @throws IllegalArgumentException if the List is null
@ -412,6 +416,7 @@ public class ListUtils {
* If the input List or predicate is null, or no element of the List
* matches the predicate, -1 is returned.
*
* @param <E> the element type
* @param list the List to search, may be null
* @param predicate the predicate to use, may be null
* @return the first index of an Object in the List which matches the predicate or -1 if none could be found