I am trying to parse some dates that are coming out of a document. It would appear users have entered these dates in a similar but not exact format.
here are the formats:
9/09
9/2009
09/2009
9/1/2009
9-1-2009
What is the best way to go about trying to parse all of these? These seem to be the most common, but I guess what is hanging me up is that if i have a pattern of "M/yyyy" wont that always catch before "MM/yyyy" Do I have to set up my try/catch blocks nested in a least restrictive to most restrictive way? it seems like it sure is going to take a lot of code duplication to get this right.
You'll need to use a different SimpleDateFormat object for each different pattern. That said, you don't need that many different ones, thanks to this:
Number: For formatting, the number of pattern letters is the minimum number of digits, and shorter numbers are zero-padded to this amount. For parsing, the number of pattern letters is ignored unless it's needed to separate two adjacent fields.
So, you'll need these formats:
"M/y" (that covers 9/09, 9/2009, and 09/2009)
"M/d/y" (that covers 9/1/2009)
"M-d-y" (that covers 9-1-2009)
So, my advice would be to write a method that works something like this (untested):
// ...
List<String> formatStrings = Arrays.asList("M/y", "M/d/y", "M-d-y");
// ...
Date tryParse(String dateString)
{
for (String formatString : formatStrings)
{
try
{
return new SimpleDateFormat(formatString).parse(dateString);
}
catch (ParseException e) {}
}
return null;
}
What about just defining multiple patterns? They might come from a config file containing known patterns, hard coded it reads like:
List<SimpleDateFormat> knownPatterns = new ArrayList<SimpleDateFormat>();
knownPatterns.add(new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'"));
knownPatterns.add(new SimpleDateFormat("yyyy-MM-dd'T'HH:mm.ss'Z'"));
knownPatterns.add(new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss"));
knownPatterns.add(new SimpleDateFormat("yyyy-MM-dd' 'HH:mm:ss"));
knownPatterns.add(new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssXXX"));
for (SimpleDateFormat pattern : knownPatterns) {
try {
// Take a try
return new Date(pattern.parse(candidate).getTime());
} catch (ParseException pe) {
// Loop on
}
}
System.err.println("No known Date format found: " + candidate);
return null;
Matt's approach above is fine, but please be aware that you will run into problems if you use it to differentiate between dates of the format y/M/d and d/M/y. For instance, a formatter initialised with y/M/d will accept a date like 01/01/2009 and give you back a date which is clearly not what you wanted. I fixed the issue as follows, but I have limited time and I'm not happy with the solution for 2 main reasons:
It violates one of Josh Bloch's quidelines, specifically 'don't use exceptions to handle program flow'.
I can see the getDateFormat() method becoming a bit of a nightmare if you needed it to handle lots of other date formats.
If I had to make something that could handle lots and lots of different date formats and needed to be highly performant, then I think I would use the approach of creating an enum which linked each different date regex to its format. Then use MyEnum.values() to loop through the enum and test with if(myEnum.getPattern().matches(date)) rather than catching a dateformatexception.
Anway, that being said, the following can handle dates of the formats 'y/M/d' 'y-M-d' 'y M d' 'd/M/y' 'd-M-y' 'd M y' and all other variations of those which include time formats as well:
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class DateUtil {
private static final String[] timeFormats = {"HH:mm:ss","HH:mm"};
private static final String[] dateSeparators = {"/","-"," "};
private static final String DMY_FORMAT = "dd{sep}MM{sep}yyyy";
private static final String YMD_FORMAT = "yyyy{sep}MM{sep}dd";
private static final String ymd_template = "\\d{4}{sep}\\d{2}{sep}\\d{2}.*";
private static final String dmy_template = "\\d{2}{sep}\\d{2}{sep}\\d{4}.*";
public static Date stringToDate(String input){
Date date = null;
String dateFormat = getDateFormat(input);
if(dateFormat == null){
throw new IllegalArgumentException("Date is not in an accepted format " + input);
}
for(String sep : dateSeparators){
String actualDateFormat = patternForSeparator(dateFormat, sep);
//try first with the time
for(String time : timeFormats){
date = tryParse(input,actualDateFormat + " " + time);
if(date != null){
return date;
}
}
//didn't work, try without the time formats
date = tryParse(input,actualDateFormat);
if(date != null){
return date;
}
}
return date;
}
private static String getDateFormat(String date){
for(String sep : dateSeparators){
String ymdPattern = patternForSeparator(ymd_template, sep);
String dmyPattern = patternForSeparator(dmy_template, sep);
if(date.matches(ymdPattern)){
return YMD_FORMAT;
}
if(date.matches(dmyPattern)){
return DMY_FORMAT;
}
}
return null;
}
private static String patternForSeparator(String template, String sep){
return template.replace("{sep}", sep);
}
private static Date tryParse(String input, String pattern){
try{
return new SimpleDateFormat(pattern).parse(input);
}
catch (ParseException e) {}
return null;
}
}
If working in Java 1.8 you can leverage the DateTimeFormatterBuilder
public static boolean isTimeStampValid(String inputString)
{
DateTimeFormatterBuilder dateTimeFormatterBuilder = new DateTimeFormatterBuilder()
.append(DateTimeFormatter.ofPattern("" + "[yyyy-MM-dd'T'HH:mm:ss.SSSZ]" + "[yyyy-MM-dd]"));
DateTimeFormatter dateTimeFormatter = dateTimeFormatterBuilder.toFormatter();
try {
dateTimeFormatter.parse(inputString);
return true;
} catch (DateTimeParseException e) {
return false;
}
}
See post: Java 8 Date equivalent to Joda's DateTimeFormatterBuilder with multiple parser formats?
In Apache commons lang, DateUtils class we have a method called parseDate. We can use this for parsing the date.
Also another library Joda-time also have the method to parse the date.
Here is the complete example (with main method) which can be added as a utility class in your project. All the format mentioned in SimpleDateFormate API is supported in the below method.
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import org.apache.commons.lang.time.DateUtils;
public class DateUtility {
public static Date parseDate(String inputDate) {
Date outputDate = null;
String[] possibleDateFormats =
{
"yyyy.MM.dd G 'at' HH:mm:ss z",
"EEE, MMM d, ''yy",
"h:mm a",
"hh 'o''clock' a, zzzz",
"K:mm a, z",
"yyyyy.MMMMM.dd GGG hh:mm aaa",
"EEE, d MMM yyyy HH:mm:ss Z",
"yyMMddHHmmssZ",
"yyyy-MM-dd'T'HH:mm:ss.SSSZ",
"yyyy-MM-dd'T'HH:mm:ss.SSSXXX",
"YYYY-'W'ww-u",
"EEE, dd MMM yyyy HH:mm:ss z",
"EEE, dd MMM yyyy HH:mm zzzz",
"yyyy-MM-dd'T'HH:mm:ssZ",
"yyyy-MM-dd'T'HH:mm:ss.SSSzzzz",
"yyyy-MM-dd'T'HH:mm:sszzzz",
"yyyy-MM-dd'T'HH:mm:ss z",
"yyyy-MM-dd'T'HH:mm:ssz",
"yyyy-MM-dd'T'HH:mm:ss",
"yyyy-MM-dd'T'HHmmss.SSSz",
"yyyy-MM-dd",
"yyyyMMdd",
"dd/MM/yy",
"dd/MM/yyyy"
};
try {
outputDate = DateUtils.parseDate(inputDate, possibleDateFormats);
System.out.println("inputDate ==> " + inputDate + ", outputDate ==> " + outputDate);
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return outputDate;
}
public static String formatDate(Date date, String requiredDateFormat) {
SimpleDateFormat df = new SimpleDateFormat(requiredDateFormat);
String outputDateFormatted = df.format(date);
return outputDateFormatted;
}
public static void main(String[] args) {
DateUtility.parseDate("20181118");
DateUtility.parseDate("2018-11-18");
DateUtility.parseDate("18/11/18");
DateUtility.parseDate("18/11/2018");
DateUtility.parseDate("2018.11.18 AD at 12:08:56 PDT");
System.out.println("");
DateUtility.parseDate("Wed, Nov 18, '18");
DateUtility.parseDate("12:08 PM");
DateUtility.parseDate("12 o'clock PM, Pacific Daylight Time");
DateUtility.parseDate("0:08 PM, PDT");
DateUtility.parseDate("02018.Nov.18 AD 12:08 PM");
System.out.println("");
DateUtility.parseDate("Wed, 18 Nov 2018 12:08:56 -0700");
DateUtility.parseDate("181118120856-0700");
DateUtility.parseDate("2018-11-18T12:08:56.235-0700");
DateUtility.parseDate("2018-11-18T12:08:56.235-07:00");
DateUtility.parseDate("2018-W27-3");
}
}
Best and Simple Java 8 answer (from https://stackoverflow.com/a/59546290/2131040)
final DateTimeFormatterBuilder dtfb = new DateTimeFormatterBuilder();
dtfb.appendOptional(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSSSSSSSS"))
.appendOptional(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSSSSSSS"))
.appendOptional(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSSSSSS"))
.appendOptional(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSSSSS"))
.appendOptional(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSSSS"))
.appendOptional(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSSS"))
.appendOptional(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS"))
.appendOptional(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SS"))
.appendOptional(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.S"))
.parseDefaulting(ChronoField.HOUR_OF_DAY, 0)
.parseDefaulting(ChronoField.MINUTE_OF_HOUR, 0)
.parseDefaulting(ChronoField.SECOND_OF_MINUTE, 0);
This solution checks all the possible formats before throwing an exception. This solution is more convenient if you are trying to test for multiple date formats.
Date extractTimestampInput(String strDate){
final List<String> dateFormats = Arrays.asList("yyyy-MM-dd HH:mm:ss.SSS", "yyyy-MM-dd");
for(String format: dateFormats){
SimpleDateFormat sdf = new SimpleDateFormat(format);
try{
return sdf.parse(strDate);
} catch (ParseException e) {
//intentionally empty
}
}
throw new IllegalArgumentException("Invalid input for date. Given '"+strDate+"', expecting format yyyy-MM-dd HH:mm:ss.SSS or yyyy-MM-dd.");
}
For the modern answer I am ignoring the requirement to use SimpleDateFormat. While using this class for parsing was a good idea in 2010 when this question was asked, it is now long outdated. The replacement, DateTimeFormatter, came out in 2014. The idea in the following is pretty much the same as in the accepted answer.
private static DateTimeFormatter[] parseFormatters = Stream.of("M/yy", "M/y", "M/d/y", "M-d-y")
.map(DateTimeFormatter::ofPattern)
.toArray(DateTimeFormatter[]::new);
public static YearMonth parseYearMonth(String input) {
for (DateTimeFormatter formatter : parseFormatters) {
try {
return YearMonth.parse(input, formatter);
} catch (DateTimeParseException dtpe) {
// ignore, try next format
}
}
throw new IllegalArgumentException("Could not parse " + input);
}
This parses each of the input strings from the question into a year-month of 2009-09. It’s important to try the two-digit year first since "M/y" could also parse 9/09, but into 0009-09 instead.
A limitation of the above code is it ignores the day-of-month from the strings that have one, like 9/1/2009. Maybe it’s OK as long as most formats have only month and year. To pick it up, we’d have to try LocalDate.parse() rather then YearMonth.parse() for the formats that include d in the pattern string. Surely it can be done.
I'm solved this problem more simple way using regex
fun parseTime(time: String?): Long {
val longRegex = "\\d{4}+-\\d{2}+-\\d{2}+\\w\\d{2}:\\d{2}:\\d{2}.\\d{3}[Z]\$"
val shortRegex = "\\d{4}+-\\d{2}+-\\d{2}+\\w\\d{2}:\\d{2}:\\d{2}Z\$"
val longDateFormat = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.sssXXX")
val shortDateFormat = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssXXX")
return when {
Pattern.matches(longRegex, time) -> longDateFormat.parse(time).time
Pattern.matches(shortRegex, time) -> shortDateFormat.parse(time).time
else -> throw InvalidParamsException(INVALID_TIME_MESSAGE, null)
}
}
Implemented the same in scala, Please help urself with converting to Java, the core logic and functions used stays the same.
import java.text.SimpleDateFormat
import org.apache.commons.lang.time.DateUtils
object MultiDataFormat {
def main(args: Array[String]) {
val dates =Array("2015-10-31","26/12/2015","19-10-2016")
val possibleDateFormats:Array[String] = Array("yyyy-MM-dd","dd/MM/yyyy","dd-MM-yyyy")
val sdf = new SimpleDateFormat("yyyy-MM-dd") //change it as per the requirement
for (date<-dates) {
val outputDate = DateUtils.parseDateStrictly(date, possibleDateFormats)
System.out.println("inputDate ==> " + date + ", outputDate ==> " +outputDate + " " + sdf.format(outputDate) )
}
}
}
Using DateTimeFormatter it can be achieved as below:
import java.text.SimpleDateFormat;
import java.time.LocalDateTime;
import java.time.ZoneOffset;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.time.temporal.TemporalAccessor;
import java.util.Date;
import java.util.TimeZone;
public class DateTimeFormatTest {
public static void main(String[] args) {
String pattern = "[yyyy-MM-dd[['T'][ ]HH:mm:ss[.SSSSSSSz][.SSS[XXX][X]]]]";
String timeSample = "2018-05-04T13:49:01.7047141Z";
SimpleDateFormat simpleDateFormatter = new SimpleDateFormat("dd/MM/yy HH:mm:ss");
DateTimeFormatter formatter = DateTimeFormatter.ofPattern(pattern);
TemporalAccessor accessor = formatter.parse(timeSample);
ZonedDateTime zTime = LocalDateTime.from(accessor).atZone(ZoneOffset.UTC);
Date date=new Date(zTime.toEpochSecond()*1000);
simpleDateFormatter.setTimeZone(TimeZone.getTimeZone(ZoneOffset.UTC));
System.out.println(simpleDateFormatter.format(date));
}
}
Pay attention at String pattern, this is the combination of multiple patterns. In open [ and close ] square brackets you can mention any kind of patterns.
I was having multiple date formats into json, and was extracting csv with universal format. I looked multiple places, tried different ways, but at the end I'm able to convert with the following simple code.
private String getDate(String anyDateFormattedString) {
#SuppressWarnings("deprecation")
Date date = new Date(anyDateFormattedString);
SimpleDateFormat dateFormat = new SimpleDateFormat(yourDesiredDateFormat);
String convertedDate = dateFormat.format(date);
return convertedDate;
}
Related
Is it possible to parse the date 8302011 using jodatime? In a less painful format, it would look like 8/30/2011, which I would pattern as MM/dd/yyyy.
What I've tried:
Pattern Mddyyyy
8302011 -> Cannot parse "8302011": Value 83 for monthOfYear must be in the range [1,12]
12302011 -> 2011-12-30T00:00:00.000Z
Fortunately, the date is not ambiguous as day is always represented as two digits. Month, however, is either one or two digits.
I realize that it would be simple enough to pad zeros on the left to 8 characters, but in this case, I am unable to do that.
I know the below is different from jodatime but can you try to use SimpleDateFormat to parse the date as an alternative one
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
/**
* Created by luan on 9/12/16.
*/
public class DateTimeFormatTest {
public SimpleDateFormat simpleDateFormat = new SimpleDateFormat("Mddyyyy");
public SimpleDateFormat simpleDateFormat2 = new SimpleDateFormat("MM/dd/yyyy");
public Date getDate(String source){
Date date = null;
try {
date = simpleDateFormat.parse(source);
} catch (ParseException e) {
e.printStackTrace();
}
return date;
}
public String parseStringValue(Date date){
String result = "";
result = simpleDateFormat2.format(date);
return result;
}
public static void main(String[] args) {
DateTimeFormatTest obj = new DateTimeFormatTest();
Date date = obj.getDate("8302011");
System.out.println(date);
String result = obj.parseStringValue(date);
System.out.println(result);
}
}
Output:
Tue Aug 30 00:00:00 ICT 2011
08/30/2011
Hi for some of the requirement i need to convert the string representation of date(with no format) to date object and convert back to string(with a specific format)
This is what i tried so far, the output is not coming as expected and it's printing something like 08140009 - Any idea what is this
And please provide any suggestions.
MY code is :
public String getDateBackToCST(String createDate){
SimpleDateFormat dateFormatter = new SimpleDateFormat("MMddyyyy");
TimeZone obj = TimeZone.getTimeZone("CST");
dateFormatter.setTimeZone(obj);
Date createdDate = null;
try {
createdDate = dateFormatter.parse(createDate);
} catch (ParseException e) {
e.printStackTrace();
}
return dateFormatter.format(createdDate);
}
You need to specific proper flags for SimpleDateFormat. You have 2 options to specify timezone z and Z and to specify day name use E like this
import java.text.ParseException;
import java.text.SimpleDateFormat;
public class Main {
public static void main(String[] args) throws ParseException {
String date = "Sat Sep 20 23:39:04 IST 2014 ";
SimpleDateFormat sdf = new SimpleDateFormat("EEE MMM dd hh:mm:ss z yyyy");
System.out.println(sdf.parse(date));
}
}
I want to convert 3/13/2014 11:38:58 AM string to date format.
I see some examples but and also implement but I don't know how to convert AM/PM to 24 hour time format.
How to make it possible ?
Use SimpleDateFormat
Date date = new SimpleDateFormat("MM/dd/yyyy hh:mm:ss a").parse(string);
Using this you can convert your date and time..
SimpleDateFormat formatter = new SimpleDateFormat("mm/dd/yyyy hh:mm:ss a");
Date date_current = new Date();
Date date_start = null;
date_start = sdf.parse("3/13/2014 11:38:58 AM");
System.out.println("now time is.." + date_start);
Thanks..
Parsing Strings into Dates:
The SimpleDateFormat class has some additional methods, notably parse( ) , which tries to parse a string according to the format stored in the given SimpleDateFormat object. For example:
import java.util.*;
import java.text.*;
public class DateDemo {
public static void main(String args[]) {
SimpleDateFormat ft = new SimpleDateFormat ("yyyy-MM-dd");
String input = args.length == 0 ? "1818-11-11" : args[0];
System.out.print(input + " Parses as ");
Date t;
try {
t = ft.parse(input);
System.out.println(t);
} catch (ParseException e) {
System.out.println("Unparseable using " + ft);
}
}
}
Using SimpleDateFormat, how can you parse the String: "2013-05-23T09:18:07 p.m..380+0000"
All my SimpleDateFormat Strings are tripping up on the "p.m." part.
Thanks in advance.
EDIT: We have no control over the format coming in.
I've tried:
"yyyy-MM-dd'T'HH:mm:ss a.a..SSSZ"
"yyyy-MM-dd'T'HH:mm:ss aaaa.SSSZ"
"yyyy-MM-dd'T'HH:mm:ss a.'m'..SSSZ"
"yyyy-MM-dd'T'HH:mm:ss a.'m.'.SSSZ"
"yyyy-MM-dd'T'HH:mm:ss a.'m..'SSSZ"
"yyyy-MM-dd'T'HH:mm:ss aa'm'..SSSZ"
"yyyy-MM-dd'T'HH:mm:ss aa'm.'.SSSZ"
"yyyy-MM-dd'T'HH:mm:ss aaa'..'SSSZ"
"yyyy-MM-dd'T'HH:mm:ss aaa.'.'SSSZ"
"yyyy-MM-dd'T'HH:mm:ss aaa'.'.SSSZ"
It's not clear what the "380+0000" part is meant to be, but you can fix the AM/PM part, by setting the DateFormatSymbols for the SimpleDateFormat. Here's an example:
import java.util.*;
import java.text.*;
public class Test {
public static void main(String[] args) throws Exception {
String text = "2013-05-23T09:18:07 p.m..380+0000";
String pattern = "yyyy-MM-dd'T'hh:mm:ss aa'.380+0000'";
SimpleDateFormat format = new SimpleDateFormat(pattern, Locale.US);
format.setTimeZone(TimeZone.getTimeZone("UTC"));
DateFormatSymbols symbols = format.getDateFormatSymbols();
symbols = (DateFormatSymbols) symbols.clone();
symbols.setAmPmStrings(new String[] { "a.m.", "p.m."});
format.setDateFormatSymbols(symbols);
Date date = format.parse(text);
System.out.println(date);
}
}
I don't know whether you have to clone the DateFormatSymbols before mutating it - it's not clear, to be honest... the documentation points two ways:
DateFormatSymbols objects are cloneable. When you obtain a DateFormatSymbols object, feel free to modify the date-time formatting data. For instance, you can replace the localized date-time format pattern characters with the ones that you feel easy to remember. Or you can change the representative cities to your favorite ones.
Given that it's mentioning cloning, that suggests you should clone - but then the subsequent paragraph suggests not :(
Here's a implementation using Java 8's new java.time package, so you can ditch java.util.Date and java.text.SimpleDateFormat:
import java.time.OffsetDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeFormatterBuilder;
import java.time.temporal.ChronoField;
import java.util.HashMap;
import java.util.Map;
public class Test {
public static void main(String[] args) {
String text = "2013-05-23T09:18:07 p.m..380+0000";
Map<Long, String> map = new HashMap<>();
map.put(0L, "a.m.");
map.put(1L, "p.m.");
DateTimeFormatter formatter = new DateTimeFormatterBuilder()
.appendPattern("yyyy-MM-dd'T'hh:mm:ss ")
.appendText(ChronoField.AMPM_OF_DAY, map)
.appendPattern(".SSSZ").toFormatter();
OffsetDateTime dateTime = OffsetDateTime.parse(text, formatter);
System.out.println(dateTime);
}
}
Running it yields:
2013-05-23T21:18:07.380Z
Do it like this
String time="2013-05-23T09:18:07 p.m..380+0000";
int index1=time.indexOf("");
int index2 = time.indexOf(".."); // or you can give p.m. as argument if you want it to stop before pm
String result = time.substring(index1,index2);
System.out.print(result);
This has the following result
2013-05-23T09:18:07 p.m
I hope this helps
Just remove the p.m. part via string manipulation. It is redundant.
Than use a simple SimpleDateFormat to do the parsing.
Something along these lines:
String whatever = "2013-05-23T09:18:07 p.m..380+0000";
whatever = whatever.replaceAll(" p.m..", ":").replaceAll(" a.m..", ":");
System.out.println(whatever);
S
String pattern = "yyyy-MM-dd'T'hh:mm:ss:SSS'Z'";
SimpleDateFormat format = new SimpleDateFormat(pattern, Locale.US);
Date date;
try {
date = format.parse(whatever);
System.out.println(date);
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Update
As pointed about by IAN, I missed out that the hours are not in 24hour format.
I did however get the millisecond part correct, and added the timezone part to Jon Skeet's answer to get:
String text = "2013-05-23T09:18:07 p.m..380+0000";
String pattern = "yyyy-MM-dd'T'hh:mm:ss aa'.'SSSZ";
SimpleDateFormat format = new SimpleDateFormat(pattern);
DateFormatSymbols symbols = format.getDateFormatSymbols();
symbols = (DateFormatSymbols) symbols.clone();
symbols.setAmPmStrings(new String[] { "a.m.", "p.m."});
format.setDateFormatSymbols(symbols);
Date date = format.parse(text);
System.out.println(date);
I'm trying to figure out a "simple" way of parsing a String into a Date Object.
The String can be either yyyyMMdd, yyyyMMddHHmm or yyyyMMddHHmmSS.
Currently, I'm looking at the length of the String, and creating a DateParser depending on the length. Is there a more elegant way of doing this?
Or you can pad your string with zeros:
SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmSS") {
#Override
public Date parse(String s) throws ParseException {
return super.parse((s + "000000").substring(0, 14));
}
};
System.out.println(sdf.format(sdf.parse("20110711182405")));
System.out.println(sdf.format(sdf.parse("201107111824")));
System.out.println(sdf.format(sdf.parse("20110711")));
I would do as you are, looking at the length of the string, and creating an appropriate SimpleDateFormat instance.
SimpleDateFormat getFormatFor( String dateString ){
if ( dateString.length() == 8 ) return new SimpleDateFormat("yyyyMMdd");
if ( dateString.length() == 14 ) return new SimpleDateFormat("yyyyMMddHHmmss");
// you got a bad input...
}
NB these are not thread-safe, so you should create a new one each time.
I would use a SimpleDateFormat class, and populate the format pattern based on the length of the string. That'll work fine unless you one day have strings of the same length.
Using the examples from your question:
Formatting 11th July 2011:
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyyMMdd");
Date parsedDate = dateFormat.parse("20110711");
Formatting 11th July 2011 1340hrs:
dateFormat = new SimpleDateFormat("yyyyMMddHHmm");
parsedDate = dateFormat.parse("201107111340");
Formatting 11th July 2011 1340hrs 10 seconds:
(NB. small s for seconds, capital S is for Milliseconds!)
dateFormat = new SimpleDateFormat("yyyyMMddHHmmss");
parsedDate = dateFormat.parse("20110711134010");
See the hyperlink for the full list of format pattern letters.
You could still used "specialized" parsers (as you suggested) and chain them:
For instance, you can still have a DateHourMinSecParser (for yyyyMMddHHmmSS), a DateHourMinParser (for yyyyMMddHHmm) and a DateParser (for yyyyMMdd) all of them implementing the same interface:
public interface GenericDateParser {
Date parseDate(String input) throws IllegalArgumentException;
}
e.g.
public class DateHourMinSecParser implements GenericDateParser {
...
public Date parseDate(String input) throws IllegalArgumentException {
...
}
}
but each one of these classes would actually take a parameter another GenericDateParser -- the idea being that each parser would try first to parse the date itself, if the parsing (or some internal checks -- e.g. string length) fails it would then pass it to the next parser in chain until either there are no more parsers in the chain (in which case it would throw an exception, or one of the members in the chain would return a value):
public class DateHourMinSecParser implements GenericDateParser {
private GenericDateParser chained;
public DateHourMinSecParser(GenericDateParser chained) {
this.chained = chained;
}
public Date parseDate(String input) throws IllegalArgumentException {
if( !internalChecks() ) { //chain it up
if( chained == null ) throw new IllegalArgumentException( "Don't know how to parse " + input);
}
//internal checks passed so try to parse it and return a Date or throw exception
...
}
}
and you would initialize them:
GenericDateParser p = new DateHourMinSecParser( new DateHourMinParser(new DateParser(null)) );
and then just use the top level one:
Date d = p.parse( '20110126' );
You can use a DateFormatter to parse the Date from the string.
import java.util.*;
import java.text.*;
public class StringToDate
{
public static void main(String[] args)
{
try
{
String str_date="11-June-07";
DateFormat formatter ;
Date date ;
formatter = new SimpleDateFormat("yyyy-MM-dd");
date = (Date)formatter.parse(str_date);
}
catch (ParseException e)
{
System.out.println("Exception :"+e);
}
}
}
You can change the pattern however you like to reflect your needs.