How to convert all String's to lower case in a collection of type HashSet <String>? : <p>I am not sure of best way to convert all Strings in a collection to lowercase. Any thoughts?</p>

<pre><code>    private Set&lt;String&gt; email;    

    if(userEmail instanceof Collection) {
    this.email = new HashSet&lt;String&gt;((Collection&lt;String&gt;) userEmail);
    model.put("userEmail", this.email); //need to convert this to lower case
}
</code></pre>

<p>Thanks in advance :-)</p>
