question: private static < T > T reportJoin ( Object r ) { if ( r instanceof AltResult ) { Throwable x ; if ( ( x = ( ( AltResult ) r ) . ex ) == null ) return null ; if ( x instanceof CancellationException ) throw ( CancellationException ) x ; if ( x instanceof CompletionException ) throw ( CompletionException ) x ; throw new CompletionException ( x ) ; } @ SuppressWarnings ( "unchecked" ) T t = ( T ) r ; return t ; }
target:  Decodes outcome to return result or throw unchecked exception.