jdk1.8新特性

╰半夏微凉° 2022-12-11 10:30 144阅读 0赞

1:取list集合某个属性的值集合

List<FanRoomSpell> spellList01 = fanRoomSpellMapper.selectFanRoomSpellList(fanRoomSpell);
    //getStudentId是获取该属性值,FanRoomSpell是此对象
    List<String> studentId01 = spellList01.parallelStream().map(FanRoomSpell::getStudentId).collect(Collectors.toList());

2:操作list排序

List<FanClassOrder> classOrderList = fanClassOrderMapper.selectFanClassOrderList(fanClassOrder);
            //根据属性值筛选符合条件的数据
    		List<FanClassOrder> newList = classOrderList.parallelStream().filter(e->e.getClassId().equals("aa")).collect(Collectors.toList());
    		FanClassOrder fanClassOrders = classOrderList.parallelStream().filter(e->e.getClassId().equals("aa")).findFirst().orElse(null);
    		//排序 加reversed是倒序
    		classOrderList.sort(Comparator.comparing(FanClassOrder::getOrderTime).reversed());

3:对map集合排序,double属性

//userList是map集合 List<Map<String,Object>> userList
    Collections.sort(userList,  new  Comparator<Map<String,Object>>() {
       @Override
       public  int  compare(Map<String, Object> o1, Map<String, Object> o2) {
          //进行判断
          Double d1 = Double.valueOf(o1.get( "salary" ).toString());
          Double d2 = Double.valueOf(o2.get( "salary" ).toString());
          return  (d2.compareTo(d1));
       }
    });

4:String 转为 List<Map<String,Object>>

/**
    	 * String 转为 List<Map<String,Object>>
    	 * @param jsonFile
    	 * @return
    	 * @throws Exception
    	 */
    	public static List<Map<String,Object>> toMapListByString(String jsonFile) throws Exception{
    		List<Object> list = JSON.parseArray(jsonFile);
    		List<Map<String,Object>> listMap = new ArrayList<Map<String,Object>>();
    		for (Object object : list) {
    			Map<String,Object> ageMap = new HashMap<String,Object>();
    			Map <String,Object> ret = (Map<String, Object>) object;//取出list里面的值转为map
    			listMap.add(ret);
    		}
    		return listMap;
    	}