WEBVTT

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Hi everyone.

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Welcome back to this tutorial.

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In this tutorial we will code and learn about DateTime formatter.

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This class is introduced in Java 1.8 and is part of the Java dot time dot format package.

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This class really made the formatting and parsing easy.

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This class is used to format and parse the local date, local time and local date and time.

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I would like to highlight the difference between the definitions of parsing and formatting here.

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Oftentimes it leads to confusion.

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Parsing in datetime formatter context refers to converting a string to a local date or local time or

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local date time formatting in DateTime formatter context refers to converting a local date or local

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time or local date time to a string.

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Before we get into the coding part, I would like to go to the Java documentation of DateTime formatter

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in their website and explain you about some of the necessary information that we have to be aware of

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when we go to the browser and then search for date time formatter and then select the first link which

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has date time formatter Java platform C eight.

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Click on that.

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This will take you to this page.

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I'm going to highlight some of the things to consider while working with DateTime formatter.

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Here.

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The first thing is it comes with some predefined constants.

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If you take a look at it, such as ISO local date, you go to this.

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This is one of the format the DateTime formatter supports by default.

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And if you take a look at the format here, followed by the month and followed by the date, if your

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use case is to convert a string to a local date and local date to a string and which is of this format,

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then you can make use of this ISO local date constant.

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And if you take a look at this example ISO offset date, it has a similar ISO local date format, but

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in addition to that it has the offset information attached to it.

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And if you take a look at ISO date, it supports both the ISO local date and the ISO offset date.

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Similar to the date it has the support for time, which is the local time and also local date time.

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I would highly recommend you guys to go through this documentation and then check whether the format

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that you are looking for is already available as part of the data formatter.

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Then you can make use of those constants in your application.

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I'm going to go to the top and then highlight some of the key things to consider while working with

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date time formatter.

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Let's go from top to bottom.

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If you are going to work with year, then you can either use U or Y.

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You're going to work with date.

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In that case, you can either use capital D or small D, The capital D represents the day of the year.

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So if you take a look at it, the number can go until 365.

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If you want to use the day of the month, then you have to use the small d you're going to work with

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month.

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In that case, you can use the capital M and you cannot use small M because small M corresponds to the

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minute of R, And if you want to work with the 24 hour format, in that case you have to use capital

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H for the 12 hours.

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You can use the small H.

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So I would highly recommend you guys to go through this because this is one of the key thing which is

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going to play a vital role while working with date time formatter.

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And it also has some reserved keywords.

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If you take a look at it, hash open curly braces and close curly braces, those you cannot use as part

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of your date time formatter pattern because those are reserved keywords.

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When I go to the IntelliJ.

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There we go.

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In here, what I'm going to do, I'm going to create a class.

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Formatting.

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Local.

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Eight.

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Example.

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And I'm going to make this class executable by adding public static void main method.

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Presentation mode.

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First thing that I'm going to do is I'm going to create two methods.

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I'm going to be public.

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Boyd.

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Going be PA's local date.

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Then the another method is going to be.

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Format.

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Local date.

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Format.

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Local date.

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So.

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Parse is like converting.

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A string to a local date.

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Right now I'm going to define a string format.

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String date is equal to.

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Zero 18 hyphen zero 428 So this is my string eight format.

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I want to convert this to a local date.

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How do I do it?

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So I'm going to create a local date instance and give it a name.

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Here what I'm going to do, I'm going to use a date time formatter.

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Dot Oh, not the date time formatter we have.

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There is a handy method called parse and local date itself.

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Local date dot parse.

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If you take a look at it, there are two different versions.

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I'm going to use the first version and then we will explore the second version in a bit.

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So in the parse, I'm going to parse this local date.

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So if we go to this, it uses something called the ISO local date format by default.

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Let's go and check what is the format.

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If you remember from our presentation, we went to the website and checked the date format.

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Right.

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So local date expects the year in four characters, followed by the dash and followed by the month in

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two characters and and a dash and followed by the day of the month in two characters.

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Does it match our actual string date format, the string date that we have?

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Yes, it does.

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Now what I'm going to do, I'm going to print this and then check.

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Being local date.

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So I'm gonna run this and check the result.

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I have not called this method yet.

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What I'm going to do, I'm going to call both the methods.

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Thus and format local date to.

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Renders.

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It is going to call this method and then print the result.

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There you go.

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It successfully converted the string to a local date.

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What is the other way of doing this?

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Let's say I'm going to use the second version of it.

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I want to pass the data formatter so we know the data formatter has a.

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It informator as a local rate.

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This is a format which we have to pass.

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We do this.

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This again equivalent to this because behind the scenes parse uses a local date.

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Here we are explicitly mentioning it.

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I'm gonna call this.

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And I'm going to print this method, print this local date one.

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Let's run this and check the result.

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There you go.

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It printed the result as expected.

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Now, let's say you have a date like this.

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Spring date one equal to.

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2018 zero 428 So this is yn y y y y.

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And then basically capitalism then.

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Right.

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So how can we parse this?

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You cannot use this.

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Have to pass a different datum parameter.

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So I'm going to change this variable name so that we can get it of the compilation issue In here, there

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is something called basic ISO date, and we covered this as part of the presentation when I talked about

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what are the different formats that it supports.

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We talked about it.

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We go here, there is no dash in between.

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Basically this is going to be here followed by the month and followed by the day of the month.

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In this.

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It is going to give me the local date instance.

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Going to copy the local data and then put it here.

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Run this and check the example.

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Check the result.

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We take a look at the result, we got into some issues.

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Let's go ahead and check it.

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What is the issue?

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The 2018?

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That is fine.

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Or here we are using the basic ISO date.

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That is also correct.

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Let's take a look at the date that we are passing.

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So here we have to pass the date one instead of date, right?

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Because we are trying to parse, we are trying to use the basic ISO date format, but we were passing

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the date as an input.

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So if you have any kind of exception when it is trying to convert a string to a date and it is not,

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if it is not able to convert, then you will get this date time parse exception.

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That is something which you have to handle it in your code.

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So now I'm going to run this.

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We run this.

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Basically, this is going to give me the result as expected.

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Take a look at it.

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It printed the result as expected.

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Now these are the predefined DateTime parameters constants, which has the predefined format in it.

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And then we have used that to convert a string to a local date.

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Now let's talk about some custom defined date format.

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Right?

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So custom find date format.

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So in here, what we are going to do, I'm going to have a date.

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Wannabe date two in here.

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What we are going to do have a date like this.

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Those in 18.

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Pipe symbol, followed by zero for pipe, symbol and 28.

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So this is our date format.

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We want to convert this to a local date.

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We take a look at the date formatter.

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There is no date format constant that supports this.

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Those kind of use cases we have to build our own.

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That's going to be date formatter.

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Give it a name then.

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DateTime formatter dot of pattern in the pattern.

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What we are going to do.

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We are going to pass the actual pattern y y y y followed by the pipe and then the month representation

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is always in capital letter that you have to be aware of.

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Followed by that we'll be passing the small d.

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So now using this, we will convert this to a local date.

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So we are going to use the same local date dot parse method.

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If you take a look at it, there is a two parameter version which takes a date and followed by the date

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time parameter.

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I'm going to pass the date to.

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And then.

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The date time format.

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You're going to give us a local date.

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Want to give it a name?

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In this and check the result.

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Going to be.

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83.

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Then Localdate three.

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Now let's run this example and check the result.

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Take a look at it.

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It successfully parsed the string to a local date.

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Now you have something like this.

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Instead of.

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The pipe.

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You have a star.

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Right.

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So in that kind of in those kind of scenarios, basically you have to build another parameter.

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Want to give it a name.

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Then the place of pipe.

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We will use Star.

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Going to be a local date.

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Played for coal to local did not pass.

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Then we are going to pass the date as date three.

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Followed by the local quarry.

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The day time formatter.

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One way date DateTime formatter one.

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Going to be local date for.

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And local date for.

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So it could parse the date as expected.

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It successfully parsed the date as expected.

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Let's say you have hash.

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Wait, we talked about it.

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Hash is something which is a reserved keyword.

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You cannot use this as part of your gate pattern.

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If I try to use it, what would happen?

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Run this and check the result.

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We take a look at it, you get an exception.

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What is that exception about?

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Legal argument exception pattern includes reserved character.

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Ash So this is something which you have to be aware of.

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So I'm going to put it back to its old value, which is.

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So these are the different examples of parsing a string to a local date.

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Now we will talk about how to convert a local date to a string.

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So what I'm going to do, I'm going to.

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Copy this pattern and put it here.

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So I have a local date instance which is going to be local date, local date, equal to local date dot

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now.

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So this is my local date.

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I want to convert this date to a string.

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How do I do it?

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So we take a look at the local date.

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There is a handy method called format and then it takes in an input called date time formatter.

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So I'm going to pass this date time formatter instance, going to give me the string as an output.

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If we go to the format method, I'm going to give it a name.

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It's going to be formatted.

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It.

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Then.

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Going to.

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You me, the date in the format that we have defined here, basically year pipe, month, pipe.

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And then.

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Eight.

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Basically the day I'm going to run this example and then check the result.

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If you take a look at the result, it's successfully converted the local date, a string which is of

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the format that we define here.

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Let's say you want.

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Start here.

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Right.

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So if I run it, the string that is going to have star in the place of.

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So this is all about converting a date to a string and string to a date using the DateTime formatter.

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Let's go ahead and explore how to convert a time to a string and string to a local time in the next

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tutorial.

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With this, we came to the end of this tutorial.

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Thank you for watching.