如何正確實現Page接口分頁，用PageImpl 自定義分頁

/**
 * Constructor of {@code PageImpl}.
 * 
 * @param content the content of this page, must not be {@literal null}.
 * @param pageable the paging information, must not be {@literal null}.
 * @param total the total amount of items available. The total might be adapted considering the length of the content
 * given, if it is going to be the content of the last page. This is in place to mitigate inconsistencies.
 */
public PageImpl(List<T> content, Pageable pageable, long total)

content：當前頁的記錄。
total：所有記錄數
也就是用PageImpl實現Page接口的時候，不能把數據全取回來放入content，得按分頁的size放入。而最后一個參數需要記錄的是所有數據的計數。

    public Page<ESIndexObject> getAllESIndex(Pageable pageable) {
        String strQuery = "/_cat/indices?v&h=uuid,health,status,index,docsCount,storeSize,cds&s=cds:desc&format=json";
        Request request = new Request("GET", strQuery);
        try {
            Response response = restClient.performRequest(request);
            String responseBody = EntityUtils.toString(response.getEntity());
            ObjectMapper mapper = new ObjectMapper();
　　　　　　
            List<ESIndexObject> list = mapper.readValue(responseBody,new TypeReference<List<ESIndexObject>>(){});
            int totalElements = list.size();
            if(pageable==null)
            {
                pageable = PageRequest.of(0,10);
            }
            int fromIndex = pageable.getPageSize()*pageable.getPageNumber();
            int toIndex = pageable.getPageSize()*(pageable.getPageNumber()+1);
            if(toIndex>totalElements) toIndex = totalElements;

　　　　　　　//如果list的內容取回后基本不變化，可以考慮放入類對象變量里或者其他緩存里，然后判斷list是否可用，不用每次都去取list，適合取數的時候無法真分頁只能偽分頁情況。
            //類似取mysql數據庫的情況，因為數據取數本身支持分頁，所以list的數據每次都取當前頁就可以，但是需要先要計算所有記錄數，然后傳入totalElements變量
            List<ESIndexObject> indexObjects = list.subList(fromIndex,toIndex);#獲取當前頁數據
            Page<ESIndexObject> page = new PageImpl<>(indexObjects,pageable,totalElements);
            return page;
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }