在Java中解析字符串中的不同日期格式

Question

I have a string which can possibly contain a date in any of the following formats:

2001-01-05 (yyyy-mm-dd)
2001/01/05 (yyyy/mm/dd)
01/05/2001 (dd/mm/yyyy)
01-05-2001 (dd-mm-yyyy)
2001 january 5
2001 5 january
january 5 2001
5 january 2001
january 5
5 january

I want to be able to parse the particular string and extract the Date object from it.

My approach was as follows:

String[] date_formats = {
                            "yyyy-MM-dd",
                            "yyyyy/MM/dd", 
                            "dd/MM/yyyyy",
                            "dd-MM-yyyy",
                            "yyyy MMM dd",
                            "yyyy dd MMM",
                            "dd MMM yyyy",
                            "dd MMM",
                            "MMM dd",
                            "dd MMM yyyy"};

String output_date = null;
for (String formatString : date_formats)
{
     try
     {    
         Date mydate = new SimpleDateFormat(formatString).parse(token);
         SimpleDateFormat outdate = new SimpleDateFormat("yyyyMMdd");
         output_date = outdate.format(mydate);
         break;
     }
     catch (ParseException e) {
         System.out.println("Next!");
     }
 }

This doesn't seem to work as expected. Especially for dates like 5 January 2001 etc. How do I go about doing this?

Answer 1

Use SimpleDateFormat.setLenient(false) . This way it will not attempt to parse dates that aren't the exact format it wants.

Answer 2

You need to have all formats in the date_formats array for the type of format you anticipate would be coming in.

Have a look at the SimpleDateFormat javadocs .

Have a look at the examples in the javadocs.

2001-01-05      - yyyy-MM-dd 
2001/01/05      - yyyy/MM/dd
01/05/2001      - dd/MM/yyyy 
01-05-2001      - dd-MM-yyyy 
2001 january 5  - yyyy MMMMM d
2001 5 january  - yyyy d MMMMM
january 5 2001  - MMMMM d yyyy 
5 january 2001  - d MMMMM yyyy
january 5       - MMMMM d
5 january       - d MMMMM

Answer 3

Instead of testing "yyyy-MM-dd", then "yyyy/MM/dd", then "yyyy.MM.dd" (used in many countries), etc., you can start by

token = token.replaceAll("-|\\.", "/");

This way all dots and dashes are replaced with "/", and you can reduce the number of formats and tries.

Answer 4

Is this what you are looking for?

String[] date_formats = {
                        "y-M-d",
                        "y/M/d", 
                        "d/M/y",
                        "d-M-y",
                        "y M d",
                        "y d M",
                        "d M y",
                        "d M",
                        "M d",
                        "d M y"};

String output_date = null;
for (String formatString : date_formats)
{
     try
     {    
         SimpleDateFormat sf = new SimpleDateFormat(formatString);  
         output_date = "5 January 2001"; 
         Date yourDate = sf.parse(output_date);
         break;
     }
     catch (ParseException e) {
         System.out.println("Next!");
     }
 }

Answer 5

You can extract String of Date by using

String mydate = new SimpleDateFormat(formatString).format(new Date());

new Date() will return current day's date, you can change it to any date that you desire.

So if you change you code like this:

String[] date_formats = {
        "y-M-d",
        "y/M/d", 
        "d/M/y",
        "d-M-y",
        "y M d",
        "y d M",
        "d M y",
        "d M",
        "M d",
        "d M y"};

for (String formatString : date_formats)
    {
        String mydate = new SimpleDateFormat(formatString).format(new Date());
        System.out.println(mydate);
    }

You will end up with these:

2013-10-2
2013/10/2
2/10/2013
2-10-2013
2013 10 2
2013 2 10
2 10 2013
2 10
10 2
2 10 2013

Answer 6

为“2001年1月5日”添加此日期格式"dd MMMMM YYYY" ”

Answer 7

SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
    String dateInString = formatter.format(date);

    LOG.warn("date in String "+dateInString);

make Sure that MM is in capital

Answer 8

Kayamans answer works, this is what it looks like in a code snippet so you can easily test it for yourself (direct copy paste from my own code):

static String[] date_formats = {
        "yyyy-MM-dd",
        "yyyy/MM/dd",
        "dd/MM/yyyy",
        "dd-MM-yyyy",
        "yyyy MMM dd",
        "yyyy dd MMM",
        "dd MMM yyyy",
        "dd MMM yyyy"};

static String[] dates = {
        "21/02/2012",
        "21-02-2012",
        "21-2-2012",
        "21 Feb 2012",
        "Feb 21 2012",//will not be parsed
        "21 februari 2012" //Dutch
};

@Test
public void test(){
    for(String date : dates) {
        parseDate(date);
        System.out.print("----------------");
    }
}

private void parseDate(String token){
    Locale dutch = new Locale("nl", "NL");
    for (String formatString : date_formats)
    {
        try
        {
            SimpleDateFormat format = new SimpleDateFormat(formatString, dutch);
            format.setLenient(false);
            Date mydate = format.parse(token);
            System.out.println(mydate.toString());
            break;
        }
        catch (ParseException e) {
            System.out.println("Next!");
        }
    }
}