How to compare LocalDateTime instances in kotlin-CodePudding

so I'm having a little problem with kotlin LocalDateTime

val now = CurrentDateTime
val someDate = someService.someLocalDateTime

I have two dates as you can see and I want to know if now is bigger than someDate or not. and also I need to know if it's bigger, how much is bigger.

i can do it by checking year, month, day, minute and second like this:

if (now.year().toString() == someDate.year.toString())

but it's not a good way

any suggesstions would be welcome.

CodePudding user response：

You can simply convert both dates in seconds and:

compare them to know which one is bigger
subtract them to know how much one is bigger than the other

an example would be

val now = CurrentDateTime.toEpochSeconds()
val someDate = someService.someLocalDateTime.toEpochSeconds();

if(now > someDate) 
//someDate is in the past
else
//someDate is in the future or both dates are equal

val distance = now-someDate

hope this helps

CodePudding user response：

The standard solution to compare two Date objects is by using the compareTo() function. It returns a value

= 0, if both dates are equal.
< 0, if date is before the specified date.
> 0, if date is after the specified date.

The following program demonstrates it:

import java.text.SimpleDateFormat
import java.util.*

 
fun main() {

    val now = CurrentDateTime  // "01/21/2023" 
    val someDate = someService.someLocalDateTime // "01/21/2020"
 
    val sdf = SimpleDateFormat("MM/dd/yyyy")
 
    val firstDate: Date = sdf.parse(now)
    val secondDate: Date = sdf.parse(someDate)
 
    val cmp = firstDate.compareTo(secondDate)
    when {
        cmp > 0 -> {
            System.out.printf("%s is after %s", d1, d2)
        }
        cmp < 0 -> {
            System.out.printf("%s is before %s", d1, d2)
        }
        else -> {
            print("Both dates are equal")
        }
    }
}

CodePudding user response：

Convert Kotlin `LocalDateTime` to Java `LocalDateTime`

To convert Kotlin LocalDateTime to Java LocalDateTime, you can make use of this function:

fun LocalDateTime.toJavaLocalDateTime(): LocalDateTime

Converts this kotlinx.datetime.LocalDateTime value to a java.time.LocalDateTime value.

And then you can choose to use the following method or other suggested method to compare the converted java.time.LocalDateTime.

Compare Java `LocalDateTime`

To compare LocalDateTime, you can use LocalDateTime's isAfter(), isBefore(), isEqual().

import java.time.LocalDateTime

fun main() {
    val currentTime = LocalDateTime.now()
    val ytdTime = LocalDateTime.now().minusDays(1)
    println(currentTime.isAfter(ytdTime))
    println(currentTime.isBefore(ytdTime))
    println(currentTime.isEqual(ytdTime))
}

Output

true
false
false

To find the difference between LocalDateTime, you can use ChronoUnit:

import java.time.temporal.ChronoUnit

fun main() {
    val currentTime = LocalDateTime.now()
    val ytdTime = LocalDateTime.now().minusDays(1)
    val secondDifference = ChronoUnit.SECONDS.between(ytdTime, currentTime)
    val minutesDifference = ChronoUnit.MINUTES.between(ytdTime, currentTime)
    val hourDifference = ChronoUnit.HOURS.between(ytdTime, currentTime)
    println(secondDifference)
    println(minutesDifference)
    println(hourDifference)
}

Output

86399
1439
23

Convert Kotlin LocalDateTime to Java LocalDateTime

Compare Java LocalDateTime

Convert Kotlin `LocalDateTime` to Java `LocalDateTime`

Compare Java `LocalDateTime`