map转list对象方法，通过stream或者iterator.key集合转list，values集合转list

川长思鸟来 2023-10-10 14:46 58阅读 0赞

// key 转 List
    List<Integer> keyList = new ArrayList<>(map.keySet());
    List<Integer> keyList2 = map.keySet().stream().collect(Collectors.toList());

// value 转 List
    List<String> valueList = new ArrayList<>(map.values());
    List<String> valueList2 = map.values().stream().collect(Collectors.toList());

// Iterator转List
    List<KeyValue> keyValueList = new ArrayList<>();
    Iterator<Integer> it = map.keySet().iterator();
    while (it.hasNext()) {
    	Integer k = (Integer) it.next();
    	keyValueList.add(new KeyValue(k, map.get(k)));
    }

// Java8 Stream
    List<KeyValue> list = map.entrySet().stream().map(c -> new KeyValue(c.getKey(), c.getValue())).collect(Collectors.toList());

业务场景转ICEDMemberVO对象：

方法一通过stream：

List<ICEDMemberVO> result = icedMemberManagementVOS.entrySet().stream().map(c -> new ICEDMemberVO(c.getKey(), c.getValue())).collect(Collectors.toList());

方法二，迭代

List<ICEDMemberVO> result = new ArrayList<>();
    Iterator<Map.Entry<Integer, List<ICEDMemberManagementVO>>> iterator = icedMemberManagementVOS.entrySet().iterator();
    while (iterator.hasNext()){
        Map.Entry<Integer, List<ICEDMemberManagementVO>> next = iterator.next();
        ICEDMemberVO icedMemberVO = new ICEDMemberVO(next.getKey(), next.getValue());
        result.add(icedMemberVO);
    }

对象实体类：

@Data
    public class ICEDMemberVO {
    
        //**成员id**//
        private Integer userId;
    
        /**内容**/
        List<ICEDMemberManagementVO> icedMemberManagementVOS;
    
        public ICEDMemberVO(Integer key, List<ICEDMemberManagementVO> value) {
            this.userId = key;
            this.icedMemberManagementVOS = value;
        }
    }