jdk8foreach 大量创建对象优化

2019-01-15 07:02:58来源：博客园阅读 ()

jdk8 foreach创建对象优化

lambda foreach 创建对象

@Async
    public void asyncFullEsDoc() {
        List<Integer> docIdList = Arrays.asList(913,914);
        if (CollectionUtil.isNotNullOrEmpty(docIdList)){
            List<Document> documents = new ArrayList<>(500);
            docIdList.forEach(docId ->{
                QueryKnowledgeDocResponse doc = synchronizeRedisBaseDoc(docId);
                if (!StringUtils.isBlank(doc)){
                    Map<String, Object> docMap = BeanToMap.objectToMap(doc);
                    Document document = new Document();
                    document.setDocumentId(docId.toString()).setDocument(docMap);
                    documents.add(document);
                }
            });

            ...
        }
    }

分析，对象释放优化

    ...
    
        List<Document> documents = new ArrayList<>(500);
            Document document = new Document();
            docIdList.forEach(docId ->{
                //用于对象释放
                document.setDocumentId(null);
                document.setDocument(null);
                QueryKnowledgeDocResponse doc = synchronizeRedisBaseDoc(docId);
                if (!StringUtils.isBlank(doc)){
                    Map<String, Object> docMap = BeanToMap.objectToMap(doc);
                    document.setDocumentId(docId.toString()).setDocument(docMap);
                    documents.add(document);
                }
            });

    ...

出现的bug，最后在addList时最后一个值覆盖了前面所有值，但是foreach中对象的每个对象值都是不同的。

分析，代码继续优化

    ...
        
    List<Document> documents = new ArrayList<>(500);
            Document document = null;
            for (Integer docId: docIdList) {
                document = new Document();
                QueryKnowledgeDocResponse doc = synchronizeRedisBaseDoc(docId);
                if (!StringUtils.isBlank(doc)){
                    Map<String, Object> docMap = BeanToMap.objectToMap(doc);
                    document.setDocumentId(docId.toString()).setDocument(docMap);
                    documents.add(document);
                }
            }
    ...

如果我还是想用lambda foreach 创建对象

    ...
        List<Document> documents = new ArrayList<>(800);
            final Document[] document = new Document[1];
            docIdList.forEach(docId ->{
                QueryKnowledgeDocResponse doc = synchronizeRedisBaseDoc(docId);
                if (!StringUtils.isBlank(doc)){
                    Map<String, Object> docMap = BeanToMap.objectToMap(doc);
                    document[0] = new Document();
                    document[0].setDocumentId(docId.toString()).setDocument(docMap);
                    documents.add(document[0]);
                }
            });
    ...