Java：将字符串转换为时间戳

Question

I have an issue while I try to convert a String to a TimeStamp. I have an array that has the date in the format of yyyy-MM-dd and I want to change in the format of yyyy-MM-dd HH:mm:ss.SSS . So, I use this code:

final String OLD_FORMAT = "yyyy-MM-dd";
final String NEW_FORMAT = "yyyy-MM-dd HH:mm:ss.SSS";
String oldDateString = createdArray[k];
String newDateString;

DateFormat formatter = new SimpleDateFormat(OLD_FORMAT);
Date d = formatter.parse(oldDateString);
((SimpleDateFormat) formatter).applyPattern(NEW_FORMAT);
newDateString = formatter.format(d);
System.out.println(newDateString);

Timestamp ts = Timestamp.valueOf(newDateString);
System.out.println(ts);

and I get the following result.

2009-10-20 00:00:00.000

2009-10-20 00:00:00.0

but when I try to simply do

String text = "2011-10-02 18:48:05.123";
ts = Timestamp.valueOf(text);
System.out.println(ts);

I get the right result:

2011-10-02 18:48:05.123

Do u know what I might be doing wrong? Thanks for the help.

Answer 1

Follow these steps for a correct result:

try {
    SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss.SSS");
    Date parsedDate = dateFormat.parse(yourString);
    Timestamp timestamp = new java.sql.Timestamp(parsedDate.getTime());
} catch(Exception e) { //this generic but you can control another types of exception
    // look the origin of excption 
}

Please note that .parse(String) might throw a ParseException .

Answer 2

import java.sql.Timestamp;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class Util {
  public static Timestamp convertStringToTimestamp(String strDate) {
    try {
      DateFormat formatter = new SimpleDateFormat("dd/MM/yyyy");
       // you can change format of date
      Date date = formatter.parse(strDate);
      Timestamp timeStampDate = new Timestamp(date.getTime());

      return timeStampDate;
    } catch (ParseException e) {
      System.out.println("Exception :" + e);
      return null;
    }
  }
}

Answer 3

I should like to contribute the modern answer. When this question was asked in 2013, using the Timestamp class was right, for example for storing a date-time into your database. Today the class is long outdated. The modern Java date and time API came out with Java 8 in the spring of 2014, three and a half years ago. I recommend you use this instead.

Depending on your situation an exact requirements, there are two natural replacements for Timestamp :

• Instant is a point on the time-line. For most purposes I would consider it safest to use this. An Instant is independent of time zone and will usually work well even in situations where your client device and your database server run different time zones.
• LocalDateTime is a date and time of day without time zone, like 2011-10-02 18:48:05.123 (to quote the question).

A modern JDBC driver (JDBC 4.2 or higher) and other modern tools for database access will be happy to store either an Instant or a LocalDateTime into your database column of datatype timestamp . Both classes and the other date-time classes I am using in this answer belong to the modern API known as java.time or JSR-310.

It's easiest to convert your string to LocalDateTime , so let's take that first:

    DateTimeFormatter formatter
            = DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss.SSS");
    String text = "2011-10-02 18:48:05.123";
    LocalDateTime dateTime = LocalDateTime.parse(text, formatter);
    System.out.println(dateTime);

This prints

2011-10-02T18:48:05.123

If your string was in yyyy-MM-dd format, instead do:

    String text = "2009-10-20";
    LocalDateTime dateTime = LocalDate.parse(text).atStartOfDay();
    System.out.println(dateTime);

This prints

2009-10-20T00:00

Or still better, take the output from LocalDate.parse() and store it into a database column of datatype date .

In both cases the procedure for converting from a LocalDateTime to an Instant is:

    Instant ts = dateTime.atZone(ZoneId.systemDefault()).toInstant();
    System.out.println(ts);

I have specified a conversion using the JVM's default time zone because this is what the outdated class would have used. This is fragile, though, since the time zone setting may be changed under our feet by other parts of your program or by other programs running in the same JVM. If you can, specify a time zone in the region/city format instead, for example:

    Instant ts = dateTime.atZone(ZoneId.of("Europe/Athens")).toInstant();

Answer 4

The easy way to convert String to java.sql.Timestamp:

Timestamp t = new Timestamp(DateUtil.provideDateFormat().parse("2019-01-14T12:00:00.000Z").getTime());

DateUtil.java:

import java.text.SimpleDateFormat;
import java.util.TimeZone;

public interface DateUtil {

  String ISO_DATE_FORMAT_ZERO_OFFSET = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'";
  String UTC_TIMEZONE_NAME = "UTC";

  static SimpleDateFormat provideDateFormat() {
    SimpleDateFormat simpleDateFormat = new SimpleDateFormat(ISO_DATE_FORMAT_ZERO_OFFSET);
    simpleDateFormat.setTimeZone(TimeZone.getTimeZone(UTC_TIMEZONE_NAME));
    return simpleDateFormat;
  }
}

Answer 5

DateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");

Date date = formatter.parse(dateString);

Timestamp timestamp = new Timestamp(date.getTime());

System.out.println(timestamp);

Answer 6

Just for the sake of completeness, here is a solution with lambda and method reference:

ISO format?

Description : The following method

• converts a String with the pattern yyyy-MM-dd into a Timestamp , if a valid input is given,
• returns a null , if a null value is given,
• throws a DateTimeParseException , if an invalid input is given

Code :

static Timestamp convertStringToTimestamp(String strDate) {
    return Optional.ofNullable(strDate) // wrap the String into an Optional
                   .map(str -> LocalDate.parse(str).atStartOfDay()) // convert into a LocalDate and fix the hour:minute:sec to 00:00:00
                   .map(Timestamp::valueOf) // convert to Timestamp
                   .orElse(null); // if no value is present, return null
}

Validation : This method can be tested with those unit tests: (with Junit5 and Hamcrest )

@Test
void convertStringToTimestamp_shouldReturnTimestamp_whenValidInput() {
    // given
    String strDate = "2020-01-30";

    // when
    final Timestamp result = convertStringToTimestamp(strDate);

    // then
    final LocalDateTime dateTime = LocalDateTime.ofInstant(result.toInstant(), ZoneId.systemDefault());
    assertThat(dateTime.getYear(), is(2020));
    assertThat(dateTime.getMonthValue(), is(1));
    assertThat(dateTime.getDayOfMonth(), is(30));
}

@Test
void convertStringToTimestamp_shouldReturnTimestamp_whenInvalidInput() {
    // given
    String strDate = "7770-91-30";

    // when, then
    assertThrows(DateTimeParseException.class, () -> convertStringToTimestamp(strDate));
}

@Test
void convertStringToTimestamp_shouldReturnTimestamp_whenNullInput() {
    // when
    final Timestamp result = convertStringToTimestamp(null);

    // then
    assertThat(result, is(nullValue()));
}

Another format?

Usually, the string to parse comes with another format. A way to deal with it is to use a formatter to convert it to another format. Here is an example:

Input: 20200130 11:30

Pattern: yyyyMMdd HH:mm

Output: Timestamp of this input

Code :

static Timestamp convertStringToTimestamp(String strDate) {
    final DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMdd HH:mm");
    return Optional.ofNullable(strDate) //
                   .map(str -> LocalDateTime.parse(str, formatter))
                   .map(Timestamp::valueOf) //
                   .orElse(null);
}

Test :

@Test
void convertStringToTimestamp_shouldReturnTimestamp_whenValidInput() {
    // given
    String strDate = "20200130 11:30";

    // when
    final Timestamp result = convertStringToTimestamp(strDate);

    // then
    final LocalDateTime dateTime = LocalDateTime.ofInstant(result.toInstant(), ZoneId.systemDefault());
    assertThat(dateTime.getYear(), is(2020));
    assertThat(dateTime.getMonthValue(), is(1));
    assertThat(dateTime.getDayOfMonth(), is(30));
    assertThat(dateTime.getHour(), is(11));
    assertThat(dateTime.getMinute(), is(30));
}

Answer 7

DateFormat formatter;
formatter = new SimpleDateFormat("dd/MM/yyyy");
Date date = (Date) formatter.parse(str_date);
java.sql.Timestamp timeStampDate = new Timestamp(date.getTime());

Answer 8

first convert your date string to date then convert it to timestamp by using following set of line

Date date=new Date();
Timestamp timestamp = new Timestamp(date.getTime());//instead of date put your converted date
Timestamp myTimeStamp= timestamp;

Answer 9

can you try it once...

String dob="your date String";
String dobis=null;
final DateFormat df = new SimpleDateFormat("yyyy-MMM-dd");
final Calendar c = Calendar.getInstance();
try {
    if(dob!=null && !dob.isEmpty() && dob != "")
    {
    c.setTime(df.parse(dob));
    int month=c.get(Calendar.MONTH);
    month=month+1;
    dobis=c.get(Calendar.YEAR)+"-"+month+"-"+c.get(Calendar.DAY_OF_MONTH);
    }

}

Answer 10

I'm sure the solution is that your oldDateString is something like "2009-10-20". Obviously this does not contain any time data lower than days. If you format this string with your new formatter where should it get the minutes, seconds and milliseconds from?

So the result is absolutely correct: 2009-10-20 00:00:00.000

What you'll need to solve this, is the original timestamp (incl. time data) before your first formatting.

Answer 11

This is what I did:

Timestamp timestamp = Timestamp.valueOf(stringValue);

where stringValue can be any format of Date/Time.