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From: Jeff Higgins <jeff@invalid.invalid>
Newsgroups: comp.lang.java.programmer
Subject: Re: what is the bettter/performant way to compare org.w3c.dom.DocumentFragment
Date: Tue, 17 Jan 2012 21:33:42 -0500
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On 01/17/2012 08:56 PM, Mausam wrote:
> On Tuesday, 17 January 2012 23:02:29 UTC+5:30, Jeff Higgins  wrote:
>> On 01/17/2012 10:03 AM, Mausam wrote:
>>> I have a java class, whose contains a DocumentFragment.
>>>
>>> In the equals method of my class, I am converting the DocumentFragment to a String and comparing an equals on the String.
>>>
>>> I know this is not the best way, because "attributes" e.g can change order in Element of DocumentFragment, or e.g documents differ only in the sequence of unordered elements.
>>>
>>> So in such cases this equality will fail.
>>>
>>> Please suggest a better approach.
>> A my class is equal to another my class if and only if ...
>
> Thanks Jeff, I understand what you mean.
>
> BTW, I was checking the API http://docs.oracle.com/javase/1.5.0/docs/api/org/w3c/dom/Node.html#isEqualNode%28org.w3c.dom.Node%29
>
> The attributes NamedNodeMaps are equal. This is: they are both null, or they have the same length and for each node that exists in one map there is a node that exists in the other map and is equal, although not necessarily at the same index.
>
>
> The childNodes NodeLists are equal. This is: they are both null, or they have the same length and contain equal nodes at the same index. Note that normalization can affect equality; to avoid this, nodes should be normalized before being compared.
>
> Here for attributes, they take care of "NOT necessarily at the same index" but in case of childNodes its not being taken care of. So if there is a sequence of unordered elements (<emp/><dept/>  and<dept/><emp/>  ) they will be treated as NOT equal.
>
> So either I iterate through each node and attribute and do a comparison. That's the fall back. But before that, I wanted to check the experts if there are better options.

Yep. I based my hair trigger response upon the .equals(Object) of the 
"known implementing classes" of Node. Sorry. I'll be interested in 
finding out the "cost" associated with Arne Vajhøj's response.