Date and calendar java

Question

class Employee
{
private Date doj;

public Employee (Date doj)
{
this.doj=doj;
}
public Date getDoj()
{
return doj;
}
}


class TestEmployeeSort
{
public static List<         


        

Answer 1

String months[] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug",
        "Sep", "Oct", "Nov", "Dec" };

Calendar calendar = Calendar.getInstance();

System.out.print("Date: ");
System.out.print(months[calendar.get(Calendar.MONTH)]);
System.out.print(" " + calendar.get(Calendar.DATE) + " ");
System.out.println(calendar.get(Calendar.YEAR));

System.out.print("Time: ");
System.out.print(calendar.get(Calendar.HOUR) + ":");
System.out.print(calendar.get(Calendar.MINUTE) + ":");
System.out.println(calendar.get(Calendar.SECOND));

calendar.set(Calendar.HOUR, 10);
calendar.set(Calendar.MINUTE, 29);
calendar.set(Calendar.SECOND, 22);

System.out.print("Updated time: ");
System.out.print(calendar.get(Calendar.HOUR) + ":");
System.out.print(calendar.get(Calendar.MINUTE) + ":");
System.out.println(calendar.get(Calendar.SECOND));

Answer 2

tl;dr

LocalDate.of( 1986 , Month.FEBRUARY , 23 )

Date-only

Neither of those classes, Date & Calendar, are suitable.

You apparently want a date-only value without a time-of-day and without a time zone. In contrast, the Date class is a date with a time-of-day in UTC, and Calendar is a date-time with a time zone.

Furthermore, both Date & Calendar are obsolete, replaced by the java.time classes.

LocalDate

The LocalDate class represents a date-only value without time-of-day and without time zone.

Today

A time zone is crucial in determining a date. For any given moment, the date varies around the globe by zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec.

If no time zone is specified, the JVM implicitly applies its current default time zone. That default may change at any moment, so your results may vary. Better to specify your desired/expected time zone explicitly as an argument.

Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).

ZoneId z = ZoneId.of( "America/Montreal" );
LocalDate today = LocalDate.now( z );  // Get current date for a particular time zone.

Specific date

Or specify a date. You may set the month by a number, with sane numbering 1-12 for January-December, unlike the crazy zero-based numbering in the legacy class.

LocalDate ld = LocalDate.of( 1986 , 2 , 23 ) ;  // Both year and month have same numbering. 1986 is the year 1986. 1-12 is January-December. 

Or, better, use the Month enum objects pre-defined, one for each month of the year. Tip: Use these Month objects throughout your codebase rather than a mere integer number to make your code more self-documenting, ensure valid values, and provide type-safety.

LocalDate ld = LocalDate.of( 1986 , Month.FEBRUARY , 23 ) ;

Strings

Generate a String representing the date value in standard ISO 8601 format by calling toString: YYYY-MM-DD. For other formats, see DateTimeFormatter class.

String output = ld.toString() ;  // Generate a string in standard ISO 8601 format, YYYY-MM-DD.

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About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

Where to obtain the java.time classes?

• Java SE 8, Java SE 9, and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and Java SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • Later versions of Android bundle implementations of the java.time classes.
  • For earlier Android, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.