<p> The return value of this method should be checked. One common
cause of this warning is to invoke a method on an immutable object,
thinking that it updates the object. For example, in the following code
fragment,</p>
<blockquote>
<pre>
String dateString = getHeaderField(name);
dateString.trim();
</pre>
</blockquote>
<p>the programmer seems to be thinking that the trim() method will update
the String referenced by dateString. But since Strings are immutable, the trim()
function returns a new String value, which is being ignored here. The code
should be corrected to: </p>
<blockquote>
<pre>
String dateString = getHeaderField(name);
dateString = dateString.trim();
</pre>
</blockquote>