[collections] ListUtil Method Proposal: isEqualUnordered

[Lukas Bradley <lu...@somnia.com>]

I needed a method like isEqualList(final Collection list1, final 
Collection list2), but did not consider order as important.

I don't know if this is a welcome addition to the ListUtil class, but I 
am posting it here to be used as desired.


    /**
     * <p>
     * Tests two lists for value-equality as per the equality contract 
in List.equals(java.lang.Object), with one
     * exception: the lists <b>do not </b> have to have the objects in 
the same order.
     * </p>
     *
     * <p>
     * The relevant text (slightly paraphrased and reworded as this is a 
static method) is:
     * </p>
     *
     * <blockquote>Compares the two list objects for equality. Returns 
true if and only if both lists have the same size,
     * and all corresponding pairs of elements in the two lists are 
equal. (Two elements e1 and e2 are equal if (e1==null ?
     * e2==null : e1.equals(e2)).) In other words, two lists are defined 
to be equal if they contain the same elements
     * <i>in any order </i>. This definition ensures that the equals 
method works properly across different
     * implementations of the List interface. </blockquote>
     *
     * <p>
     * This method iterates over all items in list one, making sure they 
are contained in list two.
     * </p>
     *
     * <p>
     * <b>Note: </b> The behaviour of this method is undefined if the 
lists are modified during the equals comparison.
     * </p>
     *
     * @param pList1
     *           The first list, may be null.
     * @param pList2
     *           The second list, may be null.
     * @return Whether the lists are equal by value comparison, 
regardless of order.
     * @see java.util.List#contains(java.lang.Object)
     */
    public static final boolean isEqualUnordered(final Collection 
pList1, final Collection pList2)
    {
       // If both lists are null, they are considered equal
       if (pList1 == pList2)
          return true;
       // If one of the lists is null, or the lists have different 
sizes, they are NOT equal
       if (pList1 == null || pList2 == null || pList1.size() != 
pList2.size())
          return false;

       Iterator it1 = pList1.iterator();
       Object obj1;
       while (it1.hasNext())
       {
          obj1 = it1.next();

          // If the object is null, or the second list does not contain 
the object, return false
          if (obj1 == null || !pList2.contains(obj1))
             return false;
       }

       return true;
    } // public static final boolean isEqualUnordered(final Collection 
pList1, final Collection pList2)


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