how to solve the error when convert string date to integer?

问题

I would like to convert my string date to int but I get an error, example of my date 'dim. janv. 23 24:00:00 +0000 2011` This is part of my code :

   String created_at =  (String) jsonObject.get("created_at");
   System.out.println("la date de création de tweet est: " + created_at);
   DateFormat df = new SimpleDateFormat(" ddd. MMMM. EE HH:mm:ss z yyyy");
   String s= df.format(created_at);
   int out=Integer.valueOf(s);
   System.out.println("new date " +out);

And the output is:

java.lang.IllegalArgumentException: Cannot format given Object as a Date.

回答1:

Well, you already have the date in String format and that's what the format method does. I am assuming what you want to do here is to parse the date (into Date object) and not format.

Also, it looks like the date is in French locale, so you need to use appropriate locale along with SimpleDateFormat and use parse method, e.g.:

DateFormat df = new SimpleDateFormat("EEE MMMM dd HH:mm:ss z yyyy", Locale.FRANCE);
Date date = df.parse("dim. janv. 23 24:00:00 +0000 2011");
System.out.println(date);

This would give you the Date object. If you want to format it differently, you can call format method with different format.

Update

Also, it looks like you are calling overloaded version of format method (by passing in a String and not a Date object. This evantually calls format method of TextFormat class (javadoc here) and that's why you get that Exception.

回答2:

I am aware that there is an accepted answer already. I am posting this to inspire you and anyone else to drop the outdated classes DateFormat and SimpleDateFormat. These days we have so much better in the modern DateTimeFormatter and friends, these classes tend to be much more programmer friendly. So use these if you can — which you can.

    System.out.println("la date de création de tweet est: " + created_at);
    DateTimeFormatter dtf = DateTimeFormatter.ofPattern("EEE MMM dd HH:mm:ss xx uuuu", 
                                                        Locale.FRENCH);
    OffsetDateTime dateTime = OffsetDateTime.parse(created_at, dtf);

This prints:

la date de création de tweet est: dim. janv. 23 24:00:00 +0000 2011
2011-01-24T00:00Z

In French the dots are part of the abbreviations for day of week and month, so they should not be explicit in the format pattern string. Also be aware that you don’t have a leading space in there (unless your date-time string has one too). The result is correct since midnight at 24 hours on 23th of January is the same as 0 hours in the 24th.

The other string from the comment, "Tue Feb 08 12:30:27 +0000 2011", is in the same format, only in English. So you need not change the format pattern, only the locale:

    DateTimeFormatter dtf = DateTimeFormatter.ofPattern("EEE MMM dd HH:mm:ss xx uuuu",
                                                        Locale.ENGLISH);

Now the result is:

la date de création de tweet est: Tue Feb 08 12:30:27 +0000 2011
2011-02-08T12:30:27Z

I didn’t understand the part about converting to integer. I noticed you tried Integer.valueOf(s) in the code in the question, which will only work if you format the date-time into a string of digits first. For example:

    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("uuuuMMdd");
    String s = dateTime.format(formatter);
    int out = Integer.parseInt(s);
    System.out.println("new date " + out);

This prints

new date 20110124

But I probably guessed incorrectly at what you are aiming at. I shall be happy to edit if you explain your requirement better. I used parseInt() en lieu of valueOf(), the result is the same, I just avoid the automatic conversion from Integer to int.

Edit: What if the date of creation of tweet is for example "dim. janv. 23 24:00:10 +0000 2011"? That is, 10 seconds past midnight. Then we get Invalid value for HourOfDay (valid values 0 - 23): 24.

While Java apparently accepts 24:00:00 as a time, it thinks that times after midnight should written as for example 0:00:10 on the following day. However, we can easily relax that requirement:

    DateTimeFormatter dtf = DateTimeFormatter.ofPattern("EEE MMM dd HH:mm:ss xx uuuu", 
                                                        Locale.FRENCH)
            .withResolverStyle(ResolverStyle.LENIENT);

Date time formatters come with three resolver styles, strict, smart (the default) and lenient. Using the last one we get

2011-01-24T00:00:10Z

Again, as expected, 24:00:10 on 23th of January equals 0:00:10 on the 24th.

来源：https://stackoverflow.com/questions/44348852/how-to-solve-the-error-when-convert-string-date-to-integer

标签

java

date-parsing