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    <p>How were you proposing to retrieve the item from the hash set? A set is by definition not ordered in any way and therefore, there is no index with which to use to retrieve the object in question.</p> <p>Sets, as a concept, are used to test inclusion, i.e. whether or not the element in question is in the hash data set. If you're looking to retrieve a value from a data source using a key value or index, I would suggest looking into either a <a href="http://java.sun.com/javase/6/docs/api/java/util/Map.html" rel="noreferrer">Map</a> or a <a href="http://java.sun.com/javase/6/docs/api/java/util/List.html" rel="noreferrer">List</a>.</p> <p><strong>EDIT: Additional answer based on the Edit to the original question</strong></p> <p>Soonil, based on your new information, it looks like you might be interested in implementing your data as a Java Enum, something similar to this:</p> <pre><code> public enum SoonilsDataType { A, B, C; // Just an example of what's possible public static SoonilsDataType getCompositeValue(SoonilsDataType item1, SoonilsDataType item2) { if (item1.equals(A) &amp;&amp; item2.equals(B)) { return C; } } } </code></pre> <p>Enum's automatically inherit values() which returns the list of all values in the enum's "set", which you can use to test inclusion against in the same way as the Set. Also, because its a full class, you can define new static methods to do the composite logic (like I was trying to allude to in the example code). The only thing about the Enum is that you can't add new instances at runtime, which may not be what you want (though if the set's data size isn't going to grow at runtime, the Enum is what you want).</p>
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    1. COSee my comment to penpen for your answer.
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    2. CO@Soonil If I understand your comment to penpen, you're using not only object equality (for existence in the Set) but also a identifier (or some other numerical index) of your own devising as a secondary equals and you want this identifier to also be used as a index into the hash set? If this is correct, you seem to be working orthogonal to the nature of hash set and I once again suggest you look into a Map (probably HashMap) as your data source.
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    3. COSure Peter, I've added some details to the end of my question, let me know if that helps.
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