From a java.util.Date( a timestamp), how can I get the hour of day?
In joda.time I use getHourOfDay().
There are multiple solutions for this. If you wish to use the Java 8 classes from java.time the following you need to covert a Date to one of the DateTime classes. The following can be used to convert a Date to a ZonedDateTime where you then can get the hour:
Date date = new Date();
// Convert to java 8 ZonedDateTime
Date date = new Date();
final ZonedDateTime dateTime = date.toInstant()
.atZone(ZoneId.systemDefault());
// Get the hour
int hour = dateTime.getHour();
Quite verbose as you have noticed but the simple reason for this is that a Date is sort of an Instant
Despite its name, java.util.Date represents an instant on the time-line, not a "date". The actual data stored within the object is a long count of milliseconds since 1970-01-01T00:00Z (midnight at the start of 1970 GMT/UTC).
Another approach is simply to get the field from a Calendar instance.
final Calendar instance = Calendar.getInstance();
instance.setTime(date);
final int hourOfDay = instance.get(Calendar.HOUR_OF_DAY);
Related
With Joda library, you can do
DateTimeFormat.forPattern("yyyy").parseLocalDate("2008")
that creates a LocalDate at Jan 1st, 2008
With Java8, you can try to do
LocalDate.parse("2008",DateTimeFormatter.ofPattern("yyyy"))
but that fails to parse:
Text '2008' could not be parsed: Unable to obtain LocalDate from TemporalAccessor: {Year=2008},ISO of type java.time.format.Parsed
Is there any alternative, instead of specifically writing sth like
LocalDate.ofYearDay(Integer.valueOf("2008"), 1)
?
LocalDate parsing requires that all of the year, month and day are specfied.
You can specify default values for the month and day by using a DateTimeFormatterBuilder and using the parseDefaulting methods:
DateTimeFormatter format = new DateTimeFormatterBuilder()
.appendPattern("yyyy")
.parseDefaulting(ChronoField.MONTH_OF_YEAR, 1)
.parseDefaulting(ChronoField.DAY_OF_MONTH, 1)
.toFormatter();
LocalDate.parse("2008", format);
String yearStr = "2008";
Year year = Year.parse(yearStr);
System.out.println(year);
Output:
2008
If what you need is a way to represent a year, then LocalDate is not the correct class for your purpose. java.time includes a Year class exactly for you. Note that we don’t even need an explicit formatter since obviously your year string is in the default format for a year. And if at a later point you want to convert, that’s easy too. To convert into the first day of the year, like Joda-Time would have given you:
LocalDate date = year.atDay(1);
System.out.println(date);
2008-01-01
In case you find the following more readable, use that instead:
LocalDate date = year.atMonth(Month.JANUARY).atDay(1);
The result is the same.
If you do need a LocalDate from the outset, greg449’s answer is correct and the one that you should use.
I didn't get you
but from the title I think you want to parse a String to a localdate so this is how you do it
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("d/MM/yyyy");
String date = "16/08/2016";
//convert String to LocalDate
LocalDate localDate = LocalDate.parse(date, formatter);
I tried like below, but in both the cases it is showing same time? What i am doing wrong.
LocalDateTime currentTime = LocalDateTime.now(ZoneId.of("UTC"));
Instant instant = currentTime.toInstant(ZoneOffset.UTC);
Date currentDate = Date.from(instant);
System.out.println("Current Date = " + currentDate);
currentTime.plusHours(12);
Instant instant2 = currentTime.toInstant(ZoneOffset.UTC);
Date expiryDate = Date.from(instant2);
System.out.println("After 12 Hours = " + expiryDate);
"Current Date" Time is showing Same as "After 12 Hours"...
The documentation of LocalDateTime specifies the instance of LocalDateTime is immutable, for example plusHours
public LocalDateTime plusHours(long hours)
Returns a copy of this LocalDateTime with the specified number of
hours added.
This instance is immutable and unaffected by this method call.
Parameters:
hours - the hours to add, may be negative
Returns:
a LocalDateTime based on this date-time with the hours added, not null
Throws:
DateTimeException - if the result exceeds the supported date range
So, you create a new instance of LocalDateTime when you execute plus operation, you need to assign this value as follows:
LocalDateTime nextTime = currentTime.plusHours(12);
Instant instant2 = nextTime.toInstant(ZoneOffset.UTC);
Date expiryDate = Date.from(instant2);
System.out.println("After 12 Hours = " + expiryDate);
I hope it can be helpful for you.
From the java.time package Javadoc (emphasis mine):
The classes defined here represent the principal date-time concepts,
including instants, durations, dates, times, time-zones and periods.
They are based on the ISO calendar system, which is the de facto world
calendar following the proleptic Gregorian rules. All the classes are
immutable and thread-safe.
Since every class in the java.time package is immutable, you need to capture the result:
LocalDateTime after = currentTime.plusHours(12);
...
This is simple, you can use
LocalDateTime's method "plusHours(numberOfHours)
Like This
localDateTime.plusHours(numberOfHours);
Is there a way to get the time in Google Glass pro grammatically? I am using System.currentTimeMillis(); but it gives me a really long number such as: 1403101657961. I want the actual time that the user is looking at when he turns on Glass. Thanks.
All you need to do is create a Date object like so:
Date dt = new Date(System.currentTimeMillis());
If you want it as a formatted string you can take a look at SimpleDateFormat.
You can use the class SimpleDateFormat to format your time to Date.
Create a date with your millisec :
Date date= new Date(System.currentTimeMillis());
then format it with SDF
new SimpleDateFormat(""yyyy.MM.dd G 'at' HH:mm:ss z").format(date)
I have two fields in my database for storing starttime and endtime. they are of datetime. I pick time from them using tostring("hh:mm tt"). Now I want to update only the time part of the date. I have dropdownlist to select hour and minutes and AM/PM. How can I update the time of date stored in sql server using Entity framework / LINQ in MVC3 application.
Please suggest
actually you don't really need to touch the linq part of this, basically what you want to do is just to convert the string back to a datetime object and just manipulate the datetime object by either creating a new datetime object or add/minus mm/dd/yy hours or minutes.
You must always update the whole datetime - it means you must build a new DateTime in your application and use correct Date part and defined Time part.
create new DateTime Object
DateTime mydate = New DateTime(2011, 6, 1, 12, 30, 0);
or
DateTime mydate = DateTime.Parse("2011-06-1 12:30:00 PM");
I have Oracle database with Date column in it and I want to retrieve it from recordset using Calendar since I want to compare it with today's date which is built using Calendar.
Not really sure what you meant with retrieving the date "using Calendar", but if you are using Java, and want to read a date from database and compare it with today's date, it goes like this:
java.sql.Date dbDate = resultset.getDate("dateField");
java.util.Date date = new Date(dbDate.getTime());
Calendar calendar = Calendar.getInstance();
java.util.Date today = calendar.getTime(); // "today = new Date();" would work just as well
if (date.before(today)) {
// do something
} else if (date.after(today)) {
// do something else
}