Java日期格式
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Java DateFormat
提问by Achilles
I know Java Date Time is not a good way to go forward but I was just curious as to what's happening:
我知道 Java Date Time 不是一个好的前进方式，但我只是对正在发生的事情感到好奇：
Why does the following line:
为什么会出现以下行：
DateFormat df = new SimpleDateFormat("dd-MMM-yyyy", Locale.US)
DateFormat df = new SimpleDateFormat("dd-MMM-yyyy", Locale.US)
not produce any errors and the following lines do:
不会产生任何错误，以下几行会：
DateFormat df = new SimpleDateFormat("DD-MMM-YYYY", Locale.US)
DateFormat df = new SimpleDateFormat("DD-MMM-YYYY", Locale.US)
DateFormat df = new SimpleDateFormat("dd-mm-YYYY", Locale.US)
DateFormat df = new SimpleDateFormat("dd-mm-YYYY", Locale.US)
The following exception gets thrown:
抛出以下异常：
Exception in thread "main" java.lang.IllegalArgumentException: Illegal pattern character 'Y'
at java.text.SimpleDateFormat.compile(SimpleDateFormat.java:769)
at java.text.SimpleDateFormat.initialize(SimpleDateFormat.java:576)
at java.text.SimpleDateFormat.<init>(SimpleDateFormat.java:501)
at testing.MySchedule.main(MySchedule.java:18)
I mean I'm just changing the case right? but is DateFormat really that dumb or am I doing something wrong? or does it have something to do with the Locale I'm using?
我的意思是我只是在改变情况，对吗？但是 DateFormat 真的那么愚蠢还是我做错了什么？还是与我使用的语言环境有关？
Cheers
干杯
采纳答案by Nikita Rybak
mand Dhave their own meaning in SimpleDateFormat pattern:
http://download.oracle.com/javase/6/docs/api/java/text/SimpleDateFormat.html
m并D在 SimpleDateFormat 模式中有自己的含义：http:
//download.oracle.com/javase/6/docs/api/java/text/SimpleDateFormat.html
m Minute in hour
D Day in year
But you won't find Yin that table.
但你不会Y在那个表中找到。
回答by cherouvim
It's not "dumb", it's just an invalid pattern. Have a look at the API: SimpleDateFormat - J2SE 6also SimpleDateFormat usage has been updated in J2SE 7 and allows using Y now SimpleDateFormat - J2SE 7
这不是“愚蠢”，它只是一个无效的模式。看看 API： SimpleDateFormat - J2SE 6SimpleDateFormat 用法也已在 J2SE 7 中更新并允许现在使用 Y SimpleDateFormat - J2SE 7
回答by Julien Hoarau
You aren't changing only the case, you are changing the meaning of the format :
您不仅在更改大小写，还更改了格式的含义：
Ydoesn't exist.Mstands for Month in yearmstands for Minute in hourDstands for Day in yeardstands for Day in month
Y不存在。M代表月份m代表分钟D代表一年中的一天d代表月中的第几天
DD-MMM-YYYYand dd-mm-YYYYformats have no meaning.
DD-MMM-YYYY和dd-mm-YYYY格式没有意义。
回答by user3215445
use (lowercase) y for year.
使用（小写）y 表示年份。
M = month
m = minute
d = 1-30 (or 31)
D = 1-365
