How can we compare ActionTimestamp and Posteventtimestamp in Java and how to update actiontimestamp to currentTimestamp

Question

How can I compare this timestamp format "20220708T0000Z" with current time and how can we update this timestamp to current time in same format in java, I have tried DateTimeFormatter and OffsetDateTime but both are not worked for me. Please help me. Here I am sharing my code:

private static final DateTimeFormatter formatter =       
                DateTimeFormatter.ofPattern("yyyyMMdd'T'HHmmssZ");


postEventInfoList.stream()
            .filter
                    (e -> e.getPostEventTimestamp() == null ||
                            ZonedDateTime.parse(e.getActionTimestamp(), 
        [1]formatter).isAfter(ZonedDateTime.parse(e.getPostEventTimestamp(), formatter)))
            .collect(Collectors.toList());


private void updatePostEventTimestamp(List<PostEventEntity> postEventInfoList) {
    ZonedDateTime timestamp = ZonedDateTime.now();
    
    postEventInfoList.forEach(pEvent -> {
        pEvent.setPostEventTimestamp(timestamp.format(formatter)); 
    });