Add new equals and hashCode methods that aid implementors of the interfaces
from Neil O'Toole git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@130990 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Stephen Colebourne
parent
a73594a4b2
commit
de8be58655
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@ -1,5 +1,5 @@
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/*
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* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/java/org/apache/commons/collections/ListUtils.java,v 1.13 2003/01/10 20:21:23 rwaldhoff Exp $
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* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/java/org/apache/commons/collections/ListUtils.java,v 1.14 2003/04/04 20:40:28 scolebourne Exp $
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* ====================================================================
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*
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* The Apache Software License, Version 1.1
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@ -69,12 +69,13 @@ import java.util.ListIterator;
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* instances.
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*
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* @since Commons Collections 1.0
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* @version $Revision: 1.13 $ $Date: 2003/01/10 20:21:23 $
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* @version $Revision: 1.14 $ $Date: 2003/04/04 20:40:28 $
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*
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* @author <a href="mailto:fede@apache.org">Federico Barbieri</a>
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* @author <a href="mailto:donaldp@apache.org">Peter Donald</a>
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* @author Paul Jack
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* @author Stephen Colebourne
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* @author Neil O'Toole
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*/
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public class ListUtils {
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@ -91,6 +92,7 @@ public class ListUtils {
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public ListUtils() {
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}
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//-----------------------------------------------------------------------
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/**
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* Returns a new list containing all elements that are contained in
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* both given lists.
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@ -169,7 +171,89 @@ public class ListUtils {
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return result;
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}
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/**
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* Tests two lists for value-equality as per the equality contract in
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* {@link java.util.List#equals(java.lang.Object)}.
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* <p>
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* This method is useful for implementing <code>List</code> when you cannot
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* extend AbstractList.
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* <p>
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* The relevant text (slightly paraphrased as this is a static method) is:
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* <blockquote>
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* Compares the two list objects for equality. Returns
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* <tt>true</tt> if and only if both
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* lists have the same size, and all corresponding pairs of elements in
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* the two lists are <i>equal</i>. (Two elements <tt>e1</tt> and
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* <tt>e2</tt> are <i>equal</i> if <tt>(e1==null ? e2==null :
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* e1.equals(e2))</tt>.) In other words, two lists are defined to be
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* equal if they contain the same elements in the same order. This
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* definition ensures that the equals method works properly across
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* different implementations of the <tt>List</tt> interface.
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* </blockquote>
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*
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* <b>Note:</b> The behaviour of this method is undefined if the lists are
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* modified during the equals comparison.
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*
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* @see java.util.List
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* @param list1 the first list, may be null
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* @param list2 the second list, may be null
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* @return whether the lists are equal by value comparison
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*/
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public static boolean equals(final List list1, final List list2) {
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if (list1 == list2) {
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return true;
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}
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if (list1 == null || list2 == null || list1.size() != list2.size()) {
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return false;
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}
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Iterator it1 = list1.iterator();
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Iterator it2 = list2.iterator();
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Object obj1 = null;
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Object obj2 = null;
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while (it1.hasNext() && it2.hasNext()) {
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obj1 = it1.next();
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obj2 = it2.next();
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if (!(obj1 == null ? obj2 == null : obj1.equals(obj2))) {
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return false;
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}
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}
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return !(it1.hasNext() || it2.hasNext());
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}
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/**
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* Generates a hashcode using the algorithm specified in
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* {@link java.util.List#hashCode()}.
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* <p>
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* This method is useful for implementing <code>List</code> when you cannot
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* extend AbstractList.
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*
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* @see java.util.List#hashCode()
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* @param list the list to generate the hashCode for, may be null
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* @return the hash code
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*/
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public static int hashCode(final List list) {
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if (list == null) {
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return 0;
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}
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int hashCode = 1;
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Iterator it = list.iterator();
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Object obj = null;
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while (it.hasNext()) {
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obj = it.next();
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hashCode = 31 * hashCode + (obj == null ? 0 : obj.hashCode());
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}
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return hashCode;
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}
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//-----------------------------------------------------------------------
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/**
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* Implementation of a ListIterator that wraps an original.
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*/
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static class ListIteratorWrapper
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implements ListIterator {
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@ -217,7 +301,9 @@ public class ListUtils {
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}
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/**
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* Implementation of a list that checks (predicates) each entry.
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*/
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static class PredicatedList
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extends CollectionUtils.PredicatedCollection
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implements List {
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@ -288,7 +374,9 @@ public class ListUtils {
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}
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/**
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* Implementation of a list that has a fixed size.
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*/
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static class FixedSizeList
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extends CollectionUtils.UnmodifiableCollection
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implements List {
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@ -356,7 +444,9 @@ public class ListUtils {
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}
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/**
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* Implementation of a list that creates objects on demand.
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*/
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static class LazyList
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extends CollectionUtils.CollectionWrapper
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implements List {
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@ -451,7 +541,7 @@ public class ListUtils {
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}
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//-----------------------------------------------------------------------
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/**
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* Returns a synchronized list backed by the given list.
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* <p>
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@ -1,5 +1,5 @@
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/*
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* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/java/org/apache/commons/collections/SetUtils.java,v 1.9 2003/01/10 20:21:23 rwaldhoff Exp $
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* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/java/org/apache/commons/collections/SetUtils.java,v 1.10 2003/04/04 20:40:28 scolebourne Exp $
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* ====================================================================
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*
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* The Apache Software License, Version 1.1
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@ -57,8 +57,10 @@
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*/
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package org.apache.commons.collections;
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import java.util.Set;
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import java.util.Collections;
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import java.util.Comparator;
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import java.util.Iterator;
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import java.util.Set;
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import java.util.SortedSet;
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import java.util.TreeSet;
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@ -67,11 +69,12 @@ import java.util.TreeSet;
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* Provides static utility methods and decorators for {@link Set}
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* and {@link SortedSet} instances.
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*
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* @version $Revision: 1.9 $ $Date: 2003/01/10 20:21:23 $
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* @version $Revision: 1.10 $ $Date: 2003/04/04 20:40:28 $
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* @since Commons Collection 2.1
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*
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* @author Paul Jack
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* @author Stephen Colebourne
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* @author Neil O'Toole
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*/
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public class SetUtils {
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@ -93,7 +96,77 @@ public class SetUtils {
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public SetUtils() {
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}
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//-----------------------------------------------------------------------
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/**
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* Tests two sets for equality as per the <code>equals()</code> contract
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* in {@link java.util.Set#equals(java.lang.Object)}.
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* <p>
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* This method is useful for implementing <code>Set</code> when you cannot
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* extend AbstractSet.
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* <p>
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* The relevant text (slightly paraphrased as this is a static method) is:
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* <blockquote>
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* <p>Two sets are considered equal if they have
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* the same size, and every member of the first set is contained in
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* the second. This ensures that the <tt>equals</tt> method works
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* properly across different implementations of the <tt>Set</tt>
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* interface.</p>
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*
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* <p>
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* This implementation first checks if the two sets are the same object:
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* if so it returns <tt>true</tt>. Then, it checks if the two sets are
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* identical in size; if not, it returns false. If so, it returns
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* <tt>a.containsAll((Collection) b)</tt>.</p>
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* </blockquote>
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*
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* @see java.util.Set
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* @param set1 the first set, may be null
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* @param set2 the second set, may be null
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* @return whether the sets are equal by value comparison
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*/
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public static boolean equals(final Set set1, final Set set2) {
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if (set1 == set2) {
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return true;
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}
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if (set1 == null || set2 == null || set1.size() != set2.size()) {
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return false;
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}
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return set1.containsAll(set2);
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}
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/**
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* Generates a hashcode using the algorithm specified in
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* {@link java.util.Set#hashCode()}.
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* <p>
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* This method is useful for implementing <code>Set</code> when you cannot
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* extend AbstractSet.
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*
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* @see java.util.Set#hashCode()
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* @param set the set to calculate the hashcode for, may be null
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* @return the hash code
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*/
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public static int hashCode(final Set set) {
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if (set == null) {
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return 0;
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}
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int hashCode = 0;
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Iterator it = set.iterator();
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Object obj = null;
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while (it.hasNext()) {
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obj = it.next();
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if (obj != null) {
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hashCode += obj.hashCode();
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}
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}
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return hashCode;
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}
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//-----------------------------------------------------------------------
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/**
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* Implementation of a set that checks new entries.
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*/
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static class PredicatedSet
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extends CollectionUtils.PredicatedCollection
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implements Set {
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@ -104,7 +177,9 @@ public class SetUtils {
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}
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/**
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* Implementation of a sorted set that checks new entries.
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*/
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static class PredicatedSortedSet
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extends PredicatedSet
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implements SortedSet {
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@ -146,6 +221,7 @@ public class SetUtils {
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}
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//-----------------------------------------------------------------------
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/**
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* Returns a synchronized set backed by the given set.
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* <p>
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@ -1,7 +1,7 @@
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/*
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* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/test/org/apache/commons/collections/TestListUtils.java,v 1.5 2002/10/12 22:36:22 scolebourne Exp $
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* $Revision: 1.5 $
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* $Date: 2002/10/12 22:36:22 $
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* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/test/org/apache/commons/collections/TestListUtils.java,v 1.6 2003/04/04 20:42:02 scolebourne Exp $
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* $Revision: 1.6 $
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* $Date: 2003/04/04 20:42:02 $
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*
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* ====================================================================
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*
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@ -61,12 +61,18 @@
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package org.apache.commons.collections;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.Collection;
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import java.util.List;
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import junit.framework.Test;
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/**
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* Tests for ListUtils.
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*
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* @author Stephen Colebourne
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* @author Neil O'Toole
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*/
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public class TestListUtils extends BulkTest {
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public TestListUtils(String name) {
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assertEquals(6, list.size());
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}
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public void testEquals() {
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Collection data = Arrays.asList( new String[] { "a", "b", "c" });
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List a = new ArrayList( data );
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List b = new ArrayList( data );
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assertEquals(true, a.equals(b));
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assertEquals(true, ListUtils.equals(a, b));
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a.clear();
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assertEquals(false, ListUtils.equals(a, b));
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assertEquals(false, ListUtils.equals(a, null));
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assertEquals(false, ListUtils.equals(null, b));
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assertEquals(true, ListUtils.equals(null, null));
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}
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public void testHashCode() {
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Collection data = Arrays.asList( new String[] { "a", "b", "c" });
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List a = new ArrayList( data );
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List b = new ArrayList( data );
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assertEquals(true, a.hashCode() == b.hashCode());
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assertEquals(true, a.hashCode() == ListUtils.hashCode(a));
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assertEquals(true, b.hashCode() == ListUtils.hashCode(b));
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assertEquals(true, ListUtils.hashCode(a) == ListUtils.hashCode(b));
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a.clear();
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assertEquals(false, ListUtils.hashCode(a) == ListUtils.hashCode(b));
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assertEquals(0, ListUtils.hashCode(null));
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}
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}
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/*
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* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/test/org/apache/commons/collections/TestSetUtils.java,v 1.3 2003/02/19 20:33:11 scolebourne Exp $
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* $Revision: 1.3 $
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* $Date: 2003/02/19 20:33:11 $
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* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/test/org/apache/commons/collections/TestSetUtils.java,v 1.4 2003/04/04 20:42:03 scolebourne Exp $
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* $Revision: 1.4 $
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* $Date: 2003/04/04 20:42:03 $
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*
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* ====================================================================
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*
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@ -60,6 +60,7 @@
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*/
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package org.apache.commons.collections;
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import java.util.Arrays;
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import java.util.Collection;
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import java.util.HashSet;
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import java.util.Set;
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@ -68,7 +69,10 @@ import junit.framework.Test;
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/**
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* Tests for SetUtils.
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* Tests for SetUtils.
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*
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* @author Stephen Colebourne
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* @author Neil O'Toole
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*/
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public class TestSetUtils extends BulkTest {
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};
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}
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public void testEquals() {
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Collection data = Arrays.asList( new String[] { "a", "b", "c" });
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Set a = new HashSet( data );
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Set b = new HashSet( data );
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assertEquals(true, a.equals(b));
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assertEquals(true, SetUtils.equals(a, b));
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a.clear();
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assertEquals(false, SetUtils.equals(a, b));
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assertEquals(false, SetUtils.equals(a, null));
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assertEquals(false, SetUtils.equals(null, b));
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assertEquals(true, SetUtils.equals(null, null));
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}
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public void testHashCode() {
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Collection data = Arrays.asList( new String[] { "a", "b", "c" });
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Set a = new HashSet( data );
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Set b = new HashSet( data );
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assertEquals(true, a.hashCode() == b.hashCode());
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assertEquals(true, a.hashCode() == SetUtils.hashCode(a));
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assertEquals(true, b.hashCode() == SetUtils.hashCode(b));
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assertEquals(true, SetUtils.hashCode(a) == SetUtils.hashCode(b));
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a.clear();
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assertEquals(false, SetUtils.hashCode(a) == SetUtils.hashCode(b));
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assertEquals(0, SetUtils.hashCode(null));
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}
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}
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