map三种赋值及map的get方法使用、Map集合一般用到的方法、map方法-处理请求参数和常用初始化方式

map三种赋值及map的get方法使用

一、map三种赋值

map String—>String
map String–>Object
map String–>List<对象>
1、
Map<Long, User> userMap = userRes.getData().stream().collect(Collectors.toMap(User::getId, i -> i));
List userChannelList = userChannelRemoteService.listAll().getData();

2、
Map<String, String> userChannelMap = userChannelList.stream()
.collect(Collectors.toMap(UserChannel::getChannelCode, UserChannel::getChannelName));

3、
if (CollectionUtil.isNotEmpty(sysDataDictList)) {
Map<String, List< SysDataDict>> map = sysDataDictList.stream()
.collect(Collectors.groupingBy(SysDataDict::getDictGroup));
map.forEach((key, value) -> {
itemConfigRespList.add(getCollectionItemConfigResp(key, value));
});
}

二、map的get方法使用

public static void main(String[] args) {
Map<Integer, Object> map = new HashMap<Integer, Object>();
map.put(1,111);
map.put(2,222);
String s = "1";
Object o = map.get(s);
sout(0)
}

Map集合一般用到的方法

public Set keySet()
将Map所有的key封装到一个Set集合
set…

public V get(Object key)
根据key获取Map对应的value
get…

public Set<Map.Entry<K,V>> entrySet()
获取所有的键值对对象集合

public Collection values()
将Map中所有的value封装到一个Collection体系的集合中

public static void main(String[] args) {
  Map<Integer, Object> map = new HashMap<Integer, Object>();
  map.put(1,111);
  map.put(2,222);
  String s = "1";
  Object o = map.get(s);
  sout(0);
  o = map.get(Long.parseLong(s));
  sout(o);
  o = map.get(Integer.parseInt(s));
  sout(o);
}

null
null
111

map方法-处理请求参数和常用初始化方式

private Map<String, String> getGeoHashHeatMapDataMap(String categoryInfo) {
    List<KeyValueData> categoryList = JSONObject.parseArray(categoryInfo, KeyValueData.class);
    Map<String, String> map = categoryList.stream()
            .collect(Collectors.toMap(KeyValueData::getK, KeyValueData::getV));
    return map;
}

List<UserCustomerServiceRecord> customerServiceRecordList =
                    userCustomerServiceRemoteService.listStaffName().getData();
            Map<String, UserCustomerServiceRecord> customerServiceRecordMap = customerServiceRecordList.stream()
                    .collect(Collectors.toMap(UserCustomerServiceRecord::getStaffId, i -> i));

分组map

Map<String, List<SysDataDict>> dictGroupMap = dictGroupList.stream()
                    .collect(Collectors.groupingBy(SysDataDict::getDictGroup));
            Map<String, List<CollectShopCompareResp.ShopTemplateDetailResp>> detailMap = openShopDetailList.stream()
                    .collect(Collectors.groupingBy(CollectShopCompareResp.ShopTemplateDetailResp::getDictGroup));

list转成map map转成list 数据结构处理

//将modelPropertyList数据结构处理成shopList
                List<CollectionItemContentResp> child = item.getChild();
                Map<String, String> childMap = child.stream()
                        .collect(Collectors.toMap(CollectionItemContentResp::getDataKey,
                                CollectionItemContentResp::getValue));
                List<BunkSaveReq> shopList = new LinkedList<>();
                Iterator<String> iterator = childMap.keySet().iterator();
                while (iterator.hasNext()) {
                    String key = iterator.next();
                    BunkSaveReq bunkSaveReq = new BunkSaveReq();
                    bunkSaveReq.setKey(key);
                    bunkSaveReq.setValue(childMap.get(key));
                    shopList.add(bunkSaveReq);
                }

list转成map
map转成list

开发尽量用map,提升代码复杂能力