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Allow passing a null array to CollectionUtil.addAll() which behaves like an

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empty array.


git-svn-id: https://samskivert.googlecode.com/svn/trunk@1953 6335cc39-0255-0410-8fd6-9bcaacd3b74c
This commit is contained in:
mdb
2006-10-17 19:21:36 +00:00
parent 13b914952d
commit 26c16e8ad4
1 changed files with 21 additions and 20 deletions
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src/java/com/samskivert/util/CollectionUtil.java
+21 -20
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@@ -32,8 +32,8 @@ import java.util.List;
public class CollectionUtil
{
/**
* Adds all items returned by the enumeration to the supplied
* collection and returns the supplied collection.
* Adds all items returned by the enumeration to the supplied collection
* and returns the supplied collection.
*/
public static <E, T extends Collection<E>> T addAll (
T col, Enumeration<E> enm)
@@ -45,8 +45,8 @@ public class CollectionUtil
}
/**
* Adds all items returned by the iterator to the supplied collection
* and returns the supplied collection.
* Adds all items returned by the iterator to the supplied collection and
* returns the supplied collection.
*/
public static <E, T extends Collection<E>> T addAll (
T col, Iterator<E> iter)
@@ -58,13 +58,16 @@ public class CollectionUtil
}
/**
* Adds all items in the given object array to the supplied
* collection and returns the supplied collection.
* Adds all items in the given object array to the supplied collection and
* returns the supplied collection. If the supplied array is null, nothing
* is added to the collection.
*/
public static <E, T extends Collection<E>> T addAll (T col, E[] values)
{
for (int ii = 0; ii < values.length; ii++) {
col.add(values[ii]);
if (values != null) {
for (int ii = 0; ii < values.length; ii++) {
col.add(values[ii]);
}
}
return col;
}
@@ -72,18 +75,16 @@ public class CollectionUtil
/**
* Returns a list containing a random selection of elements from the
* specified collection. The total number of elements selected will be
* equal to <code>count</code>, each element in the source collection
* will be selected with equal probability and no element will be
* included more than once. The elements in the random subset will
* always be included in the order they are returned from the source
* collection's iterator.
* equal to <code>count</code>, each element in the source collection will
* be selected with equal probability and no element will be included more
* than once. The elements in the random subset will always be included in
* the order they are returned from the source collection's iterator.
*
* <p> Algorithm courtesy of William R. Mahoney, published in
* <cite>Dr. Dobbs Journal, February 2002</cite>.
*
* @exception IllegalArgumentException thrown if the size of the
* collection is smaller than the number of elements requested for the
* random subset.
* @exception IllegalArgumentException thrown if the size of the collection
* is smaller than the number of elements requested for the random subset.
*/
public static <T> List<T> selectRandomSubset (Collection<T> col, int count)
{
@@ -101,10 +102,10 @@ public class CollectionUtil
for (int k = 0; iter.hasNext(); k++) {
T elem = iter.next();
// the probability that an element is select for inclusion in
// our random subset is proportional to the number of elements
// remaining to be checked for inclusion divided by the number
// of elements remaining to be included
// the probability that an element is select for inclusion in our
// random subset is proportional to the number of elements
// remaining to be checked for inclusion divided by the number of
// elements remaining to be included
float limit = ((float)(count - s)) / ((float)(csize - k));
// include the record if our random value is below the limit