Hello, We found this issue while working with LSW. It seems to be a bug in how public methods are found for inner classes. The last line of code below results in an exception rather than finding and running the size() method: ;;;---------------- (require :abcl-contrib) (require :jss) (jss::ensure-compatibility) (setq headers (#"getHeaderFields" (#"openConnection" (jss::new 'java.net.url "http://google.com")))) ; a java.util.Collections$UnmodifiableRandomAccessList (setq ural (#"get" headers (second (jss::set-to-list (#"keySet" headers))))) ;finds: #<method public int java.util.Collections$UnmodifiableCollection.size()> (find "size" (#"getMethods" (#"getClass" ural) ) :test 'string-equal :key #"getName") ; Java exception 'java.lang.NoSuchMethodException: No applicable method named size found in java.lang.Object or java.util.Collections$UnmodifiableRandomAccessList'. (#"size" ural) ;;;---------------- I chased this into org.armedbear.lisp.Java, where findMethod is returning null. - Jonathan Bona