question: boolean performWork ( TaskManager . Task who , Object param ) throws JobException { Integer tmp = null ; synchronized ( tasks ) { tmp = ( Integer ) tasks . get ( who ) ; } if ( tmp == null ) throw new UnknownTaskException ( ) ; int rank = tmp . intValue ( ) ; synchronized ( attempts ) { attempts [ rank ] ++ ; } Object result = doWork ( who , param ) ; if ( result == null ) return false ; try { reportDone ( who , result ) ; } catch ( UnknownTaskException e ) { } catch ( PartialResultException e ) { } catch ( JobException e ) { } return true ; }
target:  Used by a task to do a piece of work and record the number of attempts.