点滴-Java8的日期类

来源：互联网发布：长寿知乎编辑：程序博客网时间：2024/06/04 18:34

Java8的日期类不熟悉啊，几个小姿势记录一下。

1.LocalDate.now()不是享元

yqj2065要大量创建LocalDate对象，所以要自定义一个MyDate， public static final LocalDate today = LocalDate.now();

LocalDate d1 =LocalDate.now();
LocalDate d2 =LocalDate.now();
System.out.println(d1==d2); // false，操蛋

2.BASIC_ISO_DATE

today.format(DateTimeFormatter.ISO_DATE)为字符串 "2015-11-21"，要得到"20151121"，可以

        String dateStr = date.format(DateTimeFormatter.ISO_DATE);//BASIC_ISO_DATE        String[] d = dateStr.split("-");        String yyyymmdd = "";        for (String s : d) {            yyyymmdd += s;        }        return yyyymmdd;

但是有现成的，today.format(DateTimeFormatter.BASIC_ISO_DATE)！

3.Period

Period中，天数只管天数。

        LocalDate from = MyDate.today;        LocalDate to = from.plusDays(50);//LocalDate.of(2016, 1, 10);        Period period = from.until(to);        System.out.println(from + "  " + to + "  " + period.getDays());

有大量文件如log20151121，yqj2065要循环找到[from，to]的文件，用下面的代码：

        LocalDate from = MyDate.today;        LocalDate to = LocalDate.of(2015, 11, 25);                  List<String> fileNames = new ArrayList<>();        while(from.isBefore(to.plusDays(1))){//to]            String fileName = "log" +from.format(DateTimeFormatter.BASIC_ISO_DATE);;            fileNames.add(fileName);            from = from.plusDays(1);        }        fileNames.stream().forEach((s) -> {            System.out.println(s);        });

log20151121
log20151122
log20151123
log20151124
log20151125

不知道有没有其他的方式。

4.java.sql.Date

拼接sql：

String sql = "select  * from xxx where "                + " pin= " + boxResult.getPin() + "  AND sn= " + boxResult.getSn()                + "  AND date= '" + boxResult.getDate() + "'";

PreparedStatement：

            String condition = "insert into  xxx(orderID,customerID,pin,sn,date,outDate) values(?,?,?,?,?,?)";            PreparedStatement ps = MySQLConn.conn.prepareStatement(condition);            ps.setString(1, order.getOrderID());            ps.setInt(2, order.getCustomer().getCustomerID());            ps.setInt(3, qrCode.getPin());            ps.setInt(4, qrCode.getSN());            ps.setDate(5, java.sql.Date.valueOf(qrCode.getDate()));            ps.setDate(6, java.sql.Date.valueOf(order.getOutDate()));

这个setDate(int parameterIndex, java.sql.Date x) 有点讨嫌。为什么不提供重载的setDate(int parameterIndex, LocalDate date) ？

5.java.util.Date

老代码会遇到java.util.Date，例如使用org.jdesktop.swingx.JXDatePicker时。java.util.Date的等价物为Instant，

Date date= new Date();LocalDate localDate = date.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();

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