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copied!<p>I'm not totally sure I understand your question.</p> <p>In a standard <a href="http://docs.oracle.com/javase/6/docs/api/java/util/HashMap.html" rel="nofollow">HashMap</a>, if you put another value with the same key, it replaces the first one.</p> <p>But you may use for example a <a href="http://commons.apache.org/collections/apidocs/org/apache/commons/collections/map/MultiValueMap.html" rel="nofollow">MultiMap</a> (from Apache commons) to store more than one value per key.</p> <p>If your question is related to more than one key having the same index, this is handled by the implementation : the keys for are stored in linked lists (one for each bucket) and real comparisons (using <code>equals</code>) are done on get and put operations so that no collision can happen as long as <code>equals</code> returns false.</p> <p>As with any collection related problem, the important thing to do if you intend to use your own class is to correctly implement the <code>equals</code> and <code>hashcode</code> methods (read <a href="http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/Object.html#equals%28java.lang.Object%29" rel="nofollow">this</a>).</p> <p><strong>Regarding your question in edit :</strong></p> <p>This is a feature of HashMap that the first value with a given key is erased by the new one. So "Mexico" is removed from the HashMap when you add "New Mexico". </p> <p>If you want to have more than one value for a given key, use a MultiMap (or simply use a <code>HashMap<Integer, List<String>></code> but the <code>put</code> operation is a little more tedious).</p>

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