Java 8 Date and Time: Construction, Get and Set

This Java tutorial is to introduce the Java SE 8 Date and Time API. For long Java developers were not happy about the date and time support in the API. Main reason were the API was not consistent in its design, required numerous casting and conversions to achieve basic use case, not thread safe, etc. These were carefully looked at and mitigated in this new Java 8 API design.

In the list of Java 8 features, Date and Time API is going to be the most used by Java developers. JSR 301 is the Java Specification Request of Date and Time API release with Java SE 8. Stephen Colebourne (author of Joda Time) is one of the specification leads.

Construction Date and Time Objects

Constructing date and time objects have become easy and usable.

package com.javapapers.java8.dateandtime;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.Month;

public class DateAndTime {
	public static void main(String args[]) {
		// current date
		LocalDateTime currentDateTime = LocalDateTime.now();
		System.out.println(currentDateTime);

		// create date from passed parameters
		LocalDate date1 = LocalDate.of(2012, Month.DECEMBER, 12);
		System.out.println(date1);

		// create time from passed parameters
		LocalTime time1 = LocalTime.of(18, 30);
		System.out.println(time1);

		// parse time from a string
		LocalTime time2 = LocalTime.parse("10:15:30");
		System.out.println(time2);
	}
}

Output is:

2014-08-04T17:28:30.003 
2012-12-12 
18:30 
10:15:30

Get Date and Time

Before Java 8, to get the current month in an integer variable, we need to cross seven mountains and seas. Not its just in the calling distance.

package com.javapapers.java8.dateandtime;

import java.time.LocalDateTime;
import java.time.Month;

public class GetDateAndTime {
	public static void main(String... args) {
		LocalDateTime currentDateTime = LocalDateTime.now();
		System.out.println("Current local date and time: " + currentDateTime);
		Month month = currentDateTime.toLocalDate().getMonth();
		System.out.println("Month: "+month);
		int day = currentDateTime.toLocalDate().getDayOfMonth();
		System.out.println("Day: "+day);
		int secs = currentDateTime.getSecond();
		System.out.println("Current second: "+secs);
	}
}

Output:

Current local date and time: 2014-08-04T17:36:10.814 
Month: AUGUST 
Day: 4 
Current second: 10

Calculate /Set Date and Time

This is a real killer. Think about how we will add some X number of days to the current month before Java 8. All classes in Java 8 Date and Time API are immutable. For any operation a new instance will be returned.

package com.javapapers.java8.dateandtime;

import java.time.LocalDateTime;

public class CalculateDateAndTime {
	public static void main(String... args) {
		LocalDateTime currentDateTime = LocalDateTime.now();
		LocalDateTime lastYear = currentDateTime.withYear(2013);
		System.out.println("Same day last year: " + lastYear);
		LocalDateTime lastYearPlusOneWeek = lastYear.plusWeeks(1);
		System.out.println("Same day last year with one week added: "
				+ lastYearPlusOneWeek);
		LocalDateTime tenYrFromNow = currentDateTime.plusYears(10);
		System.out.println("Ten years from now: " + tenYrFromNow);
	}
}

Output:

Same day last year: 2013-08-04T17:46:41.371
Same day last year with one week added: 2013-08-11T17:46:41.371
Ten years from now: 2024-08-04T17:46:41.371