question: public static Long toLong ( Object o , Long defaultValue ) { if ( o instanceof Long ) return ( Long ) o ; if ( defaultValue != null ) return Long . valueOf ( toLongValue ( o , defaultValue . longValue ( ) ) ) ; long res = toLongValue ( o , Long . MIN_VALUE ) ; if ( res == Long . MIN_VALUE ) return defaultValue ; return Long . valueOf ( res ) ; }
target:  cast a Object to a Long Object(reference type)