How to replace getDate() from the type Date which is deprecated?

问题

I have an existing program that I have to correct . It contains these lines :

        Date startDate = new Date();
        int day = startDate.getDate() - 1;

but getDate() from the type Date is deprecated so i have to change it using Calender. I tried this :

Calendar startDate = Calendar.getInstance();
startDate.add(Calendar.DATE, -1);
int day= startDate.getTime();

but this results into following error :

Type mismatch: cannot convert from Date to int

回答1:

If you want to get day in month use this:

int day= startDate.get(Calendar.DAY_OF_MONTH);

If you want to get day in week use this:

int day= startDate.get(Calendar.DAY_OF_WEEK);

Also be careful about day of week, because day 0 is sunday not monday.

Field number for get and set indicating the day of the week. This field takes values SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, and SATURDAY.

回答2:

One more good option is to use like :

System.out.println(DateFormat.getDateInstance().format(new Date()));

It will print the current date.

If you need time along with date then you can use like :

System.out.println(DateFormat.getDateTimeInstance().format(new Date()));

回答3:

Type mismatch: cannot convert from Date to int

change

  int day= startDate.getTime();

to

 Date dat= startDate.getTime();//return type Date

回答4:

As the javadocs suggest, use Calendar.get(Calendar.DAY_OF_MONTH)

回答5:

To get the day of the month:

int day= startDate.get(Calendar.DAY_OF_MONTH);

From the Javadocs:

Field number for get and set indicating the day of the month. This is a synonym for DATE. The first day of the month has value 1.

回答6:

The getTime() function will return a Date Object which cannot be converted to int. If you want to get the day as an integer, you have to use:

int day = startDate.get(Calendar.DATE)

回答7:

In Date#startDate.getDate() returns the day of the month :

• Code#1-->

  Date startDate = new Date();
  int day = startDate.getDate() - 1;
  System.out.println(day); 
  

Through Calendar#.get(Calendar.DAY_OF_MONTH) you will get the same result as Date#startDate.getDate():

• Code#2-->

  Calendar startDate = Calendar.getInstance();
  int day= startDate.get(Calendar.DAY_OF_MONTH)-1;
  System.out.println(day);
  

So you can replace Code#1 by Code#2

回答8:

See on java doc at http://docs.oracle.com/javase/7/docs/api/java/util/Date.html#getTime():

Date object of getTime() method return long not in int so use like:

long time = startDate.getTime();

For Calendar docs http://docs.oracle.com/javase/7/docs/api/java/util/Calendar.html#getTime() Use like below:

long time = startDate.getTime().getTime();

For day of month:

Calendar c = Calendar.getInstance();
int dayOfMonth = c.get(Calendar.DATE);

回答9:

java.time

The old java.util.Date/.Calendar classes are notoriously troublesome. They have been supplanted in Java 8 and later by the new java.time framework.

Note the use of time zone. Crucial in determining a date. If omitted, you implicitly rely on the JVM’s current default time zone. Better to specify the desired/expected time zone.

ZoneId zoneId = ZoneId.of( "America/Montreal" );
ZonedDateTime now = ZonedDateTime.now( zoneId );
int dayOfMonth = now.getDayOfMonth();
int dayOfWeek = now.getDayOfWeek().getValue();
int dayOfYear = now.getDayOfYear();

回答10:

Simply type int day = startDate.get(Calendar.DAY_OF_WEEK);

来源：https://stackoverflow.com/questions/32694110/how-to-replace-getdate-from-the-type-date-which-is-deprecated