Java Solutions: DateFormat

Wednesday, April 9, 2014

Creating and converting Date and Time in Java 8

The new Date and Time API in java 8 makes it much easier to create, manipulate, and convert Date related objects. Classes in this new addition such as LocalDate, LocalDateTime, and LocalDateTimeFormatter are very convenient to use.

1. Creating a date

a). Current date without hour, minute, and second
LocalDate date = LocalDate.now();
b). Current date with hour, minute, and second
LocalDateTime dateTime = LocalDateTime.now();
c). A date with given year, month and dayOfMonth
int year = 2013;
int month = 11;
int dayOfMonth = 22;
LocalDate date2 = LocalDate.of (year, month, dayOfMonth);
d). A date with given year, month, dayOfMonth, hour, minute, second, and nanosecond
int year = 2013;
int month = 11;
int dayOfMonth = 22;
int hour = 21, minute = 15, second = 50;
LocalDateTime dateTime2 = LocalDateTime.of (year, month, dayOfMonth, hour, minute, second);

2. Finding a date

LocalDate date = <your date>;
To find next Saturday,
LocalDate nextSaturday = date.with(TemporalAdjusters.next(DayOfWeek.SATURDAY));

3. Converting a String to a date

a). String dateString = "<your date>"; //e.g "11/22/2013"
DateTimeFormatter pattern = DateTimeFormatter.ofPattern("<pattern of your date string>"); //e.g "MM/dd/yyyy"
LocalDate date = LocalDate.parse(dateString, pattern);
b). String dateTimeString = "<your dateTime>"; //e.g "11/22/2013 21:15:50"
DateTimeFormatter pattern = DateTimeFormatter.ofPattern("<pattern of your date string>"); //e.g "MM/dd/yyyy HH:mm:ss"
LocalDateTime dateTime = LocalDateTime.parse(dateTimeString, pattern);

4. Converting date Format

a). Converting to "MM/dd/yyyy HH:mm:ss" format, e.g "11/22/2013 21:15:50"
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MM/dd/yyyy HH:mm:ss");
String formattedDate = formatter.format(dateTime2);
b). Converting to "MM/dd/yyyy hh:mm:ss aa" format, e.g "11/22/2013 09:15:50 PM"
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MM/dd/yyyy hh:mm:ss aa");
String formattedDate = formatter.format(dateTime2);

References:
1. Convert Date format
2. Oracle: LocalDate

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Tuesday, March 4, 2014

Convert Date format

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class Test2 {

public static void main(String[] args) {
Calendar calendar = Calendar.getInstance();
//set date to 2014, January 12 16:25:20
calendar.set(2014, 0, 12, 16, 25, 20);
Date date = calendar.getTime();

//format to MM/dd/YYY HH:mm.ss (24 hour format)
SimpleDateFormat sdf1 = new SimpleDateFormat("MM/dd/YYY HH:mm.ss");
String dateString = sdf1.format(date);
System.out.println(dateString);

//format to MM/dd/YYY hh:mm.ss aa (12 hour format)
sdf1 = new SimpleDateFormat("MM/dd/YYY hh:mm.ss aa");
dateString = sdf1.format(date);
System.out.println(dateString);
}

}

Reference:

1. SimpleDateFormat
2. Creating and converting Date and Time in Java 8

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