'uuuu' versus 'yyyy' in DatetimeFormatter in java

Learn to parse date and time strings into instances of LocalDate and LocalDateTime using strict style using ResolverStyle.STRICT parameter with DateTimeFormatter instance.

ResolverStyle – Parsing styles

Parsing a string to date in Java happens in two phases:

• ResolverStyle is an enum and used to control how phase 2, resolving, happens. It contains three styles of parsing:

STRICT

public static final ResolverStyle STRICTStyle to resolve dates and times strictly.

Using strict resolution will ensure that all parsed values are within the outer range of valid values for the field. Individual fields may be further processed for strictness.

For example, resolving year-month and day-of-month in the ISO calendar system using strict mode will ensure that the day-of-month is valid for the year-month, rejecting invalid values.

//Example of yyyy

fun main() {

println(DateTimeFormatter.ofPattern("dd/MM/yyyy").withResolverStyle(ResolverStyle.STRICT).parse("31/02/2023"));
}

//Example of uuuu with ResolverStyle property

fun main() {
    
println(DateTimeFormatter.ofPattern("dd/MM/uuuu").withResolverStyle(ResolverStyle.STRICT).parse("31/02/2023"));
}

// Format using 'uuuu'

fun main() {

    println(DateTimeFormatter.ofPattern("dd/MM/uuuu").parse("31/02/2023"));
}