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COLLECTIONS-697: Ensure FixedSizeList respects underlying list's size 

Formally document and test that if the size of the backing list of
FixedSizeList changes, then so does the FixedSizeList. This has been the
historical behavior. Letting it be part of the contract is reasonable,
expected, and worthwhile to note.

Fixes #55
This commit is contained in:
george-ranjan 2018-10-02 23:14:07 +05:30 committed by Eitan Adler
parent d6800c606c
commit 74ad211470
2 changed files with 22 additions and 0 deletions
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5
src/main/java/org/apache/commons/collections4/list/FixedSizeList.java
View File

@ -31,6 +31,11 @@ import org.apache.commons.collections4.iterators.UnmodifiableIterator;
* The add, remove, clear and retain operations are unsupported.
* The set method is allowed (as it doesn't change the list size).
* <p>
* NOTE:
* Modifying the decorated list directly would results in influencing the outcome
* of method calls on this object. For example, the bounds of this list would reflect
* a newly added object to the underlying list.
* <p>
* This class is Serializable from Commons Collections 3.1.
*
* @param <E> the type of elements in this collection

17
src/test/java/org/apache/commons/collections4/list/FixedSizeListTest.java
View File

@ -16,6 +16,8 @@
*/
package org.apache.commons.collections4.list;
import org.junit.Assert;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
@ -66,4 +68,19 @@ public class FixedSizeListTest<E> extends AbstractListTest<E> {
// writeExternalFormToDisk((java.io.Serializable) getCollection(), "src/test/resources/data/test/FixedSizeList.fullCollection.version4.obj");
// }
public void testListAllowsMutationOfUnderlyingCollection() {
List<String> decoratedList = new ArrayList<>();
decoratedList.add("item 1");
decoratedList.add("item 2");
//
FixedSizeList<String> fixedSizeList = FixedSizeList.fixedSizeList(decoratedList);
int sizeBefore = fixedSizeList.size();
//
boolean changed = decoratedList.add("New Value");
Assert.assertTrue(changed);
//
Assert.assertEquals("Modifying an the underlying list is allowed",
sizeBefore + 1, fixedSizeList.size());
}
}