Users should provide classpath for RedundantThrows.

docs/config_coding.html

@@ -860,6 +860,12 @@ public class MySingleton
     <property name="allowUnchecked" value="true"/>
 </module>
       </pre>
+        <h4>Note</h4>
+
+        <p class="body">The classpath should be configured to locate the class
+        information. The classpath configuration is dependent on the
+        mechanism used to invoke Checkstyle.</p>
+
       <h4>Package</h4>
       <p class="body">
       com.puppycrawl.tools.checkstyle.checks.coding