Java8-无限流补全日期，折线图补零

原始数据

自2020-11-27 过去一周的数据，日期不连续

补全日期数据，没有的日期，数据默认补0

/**
* 折线图数据
*
* @param preDate 开始日期，不传默认近一周
* @return
*/
public List<DailyDataChartVo> getChartData(LocalDate preDate) {
if (Objects.isNull(preDate)) {
preDate = LocalDate.now().minusWeeks(1);
    }
LocalDate endDate = LocalDate.now();
List<DailyDataChartVo> list = this.dailyDataMapper.selectChartData(preDate, endDate);
return this.completeData(preDate, endDate, list);
}

/**
* 补全数据
*
* @param preDate 开始日期
* @param endDate 截止日期
* @param oldList 未补全的列表
* @return 补全后的列表
*/
private List<DailyDataChartVo> completeData(LocalDate preDate, LocalDate endDate, List<DailyDataChartVo> oldList) {
List<DailyDataChartVo> newList = new ArrayList<>();
if (CollectionUtils.isEmpty(oldList)) {
return newList;
    }
//间隔的日期列表
List<LocalDate> dates = this.getRangeDays(preDate, endDate);
Map<LocalDate, DailyDataChartVo> map = oldList.stream()
            .collect(Collectors.toMap(DailyDataChartVo::getDate, Function.identity()));
dates.forEach(c -> {
if (map.containsKey(c)) {
newList.add(map.get(c));
        } else {
//没有这一天的数据，默认补0
newList.add(new DailyDataChartVo(c, BigDecimal.ZERO));
        }
    });
return newList;
}

/**
* 获取间隔的日期列表
*
* @param preDate 开始日期
* @param endDate 截止日期
* @return
*/
private List<LocalDate> getRangeDays(LocalDate preDate, LocalDate endDate) {
List<LocalDate> dates = new ArrayList<>();
//间隔的天数
long betweenDays = ChronoUnit.DAYS.between(preDate, endDate);
if (betweenDays < 1) {
//开始日期<=截止日期
return dates;
    }
//创建一个从开始日期、每次加一天的无限流，限制到截止日期为止
Stream.iterate(preDate, c -> c.plusDays(1))
            .limit(betweenDays + 1)
            .forEach(dates::add);
return dates;
}

      

补全后的数据

点击查看代码

[
    {
        "date": "2020-11-20",
        "revenue": 22.88
    },
    {
        "date": "2020-11-21",
        "revenue": 93.06
    },
    {
        "date": "2020-11-22",
        "revenue": 0
    },
    {
        "date": "2020-11-23",
        "revenue": 7.99
    },
    {
        "date": "2020-11-24",
        "revenue": 0
    },
    {
        "date": "2020-11-25",
        "revenue": 50.98
    },
    {
        "date": "2020-11-26",
        "revenue": 0
    },
    {
        "date": "2020-11-27",
        "revenue": 0
    }
]

      

核心方法

Stream.iterate()：接收一个初始元素seed，生成从seed到f的迭代流

/**
* @param seed 初始元素
* @param f UnaryOperator，函数式接口，接收T类型参数，调用apply后返回T本身，应用于上一个元素以产生新元素
*/
public static<T> Stream<T> iterate(final T seed, final UnaryOperator<T> f) {}

//创建一个从开始日期、每次加一天的无限流，限制到截止日期为止
Stream.iterate(preDate, c -> c.plusDays(1))
        .limit(betweenDays + 1)
        .forEach(dates::add);
      

作者：cchilei

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个性签名：竹杖芒鞋轻胜马 一蓑烟雨任平生