Java Tutorials

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Java 8 Date Time Classes

LocalTime class Usage

   LocalTime represents a time without a timezone information. Human readable format(HH:mm:ss) in terms of Hours,Minutes,Seconds and nano seconds, By Default hours are represented in 24hours format. If user has time in AM/PM format, it can be parased using parse factory method.

Basic units of LocalTime and their Ranges

• Hour range 0 to 23
• Minute range 00 to 59
• Second range 00 to 59
• Nano Seconds range 00 to 999,999,999

Using static fields

      		LocalTime tm = LocalTime.MAX;

      		System.out.println(tm);
      		23:59:00.999999999

      		LocalTime tm =LocalTime.MIN;

      		System.out.println(tm);
      		00:00

      		LocalTime tm = LocalTime.NOON;
      		
      		System.out.println(tm);
      		12:00
      

Using static methods like now,of,from

now method can be used to create LocalTime object,which returns system's time

      		LocalTime tm = LocalTime.now();

      		System.out.println(tm);
      		09:02:34.947022
      

Convert String to LocalTime Object using parse method

     If time represented in string format for example reading from text file or csv file or excel file, it can be easily converted into LocalTime object using parse method, as shown below

DateTimeFormat symbols

H hour of a day	0-23
m minute	0-59
s for second	0-59
n nano of second	0
N nano of the day	0-999999999
K hour of am pm	0-11
a am-pm-of day	PM

	Using Human readable format hours:minutes:seconds using default parse method
	LocalTime tm =  LocalTime.parse("19:33:59")
	System.out.println(tm)
	19:33:59

	Parsing default format hours:minutes:seconds using DateTimeFormatter class

	DateTimeFormatter fmt = DateTimeFormatter.ofPattern("H:m:s")

	String str="12:55:59"

	LocalTime tm = LocalTime.parse(str,fmt)
	System.out.println(tm);
	12:55:59

	str="01:55:59 PM"

	Parsing hours:minutes:seconds AM/PM  formatted data using DateTimeFormatter class

	DateTimeFormatter fmt = DateTimeFormatter.ofPattern("K:m:s a")
	LocalTime tm = LocalTime.parse(str,fmt)
	System.out.println(tm);
	13:55:59

Convert LocalTime into Seconds

     LocalTime object can be converted into seconds of the day. i.e seconds elapsed since day start(mid night)

toSecondOfDay() method used to convert LocalTime Object into seconds, as shown below

		LocalTime tm = tm=LocalTime.now()
		System.out.println(tm)
		18:48:56.618730
		
		 Convert LocalTime into seconds
		int seconds = tm.toSecondOfDay();
		System.out.println(seconds)
		67736
		
		67736 seconds calculated as 
			18*60*60
			+48*60
			+56
	              = 67736  seconds
	              
	        18 hours converted into seconds , every hour has 60 minutes, every minute has 60 seconds, so 18*60*60
	        48 minutes converted into seconds 48*60
	        plus 56 seconds	
	

Convert LocalTime into String using format method

     LocalTime object can be converted into string using DateTimeFormatter and format methods.

format(DateTimeFormatter) method used to convert LocalTime Object into String, as shown below

Converting 24-hour time format into AM/PM format.

		LocalTime tm = tm=LocalTime.now()
		System.out.println(tm)
		18:48:56.618730
		
	DateTimeFormatter fmt = DateTimeFormatter.ofPattern("K:m:s a")
	
	String str = tm.format(fmt);
	System.out.println(str);
	"6:48:56 PM"
	
	// 18:48:56.618730  converted into  6:48:56 PM format