ZonedDateTime with offset and zone ID

Scratch

import static java.time.temporal.ChronoField.DAY_OF_MONTH;
import static java.time.temporal.ChronoField.HOUR_OF_DAY;
import static java.time.temporal.ChronoField.MINUTE_OF_HOUR;
import static java.time.temporal.ChronoField.MONTH_OF_YEAR;
import static java.time.temporal.ChronoField.NANO_OF_SECOND;
import static java.time.temporal.ChronoField.SECOND_OF_MINUTE;
import static java.time.temporal.ChronoField.YEAR;

import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeFormatterBuilder;
import java.time.format.ResolverStyle;
import java.time.format.SignStyle;
import java.util.Locale;
import java.util.Objects;

class Scratch {
	private static final DateTimeFormatter FORMATTER = new DateTimeFormatterBuilder()
			.appendValue( YEAR, 4, 9, SignStyle.EXCEEDS_PAD )
			.appendLiteral( '-' )
			.appendValue( MONTH_OF_YEAR, 2 )
			.appendLiteral( '-' )
			.appendValue( DAY_OF_MONTH, 2 )
			.appendLiteral( 'T' )
			.appendValue( HOUR_OF_DAY, 2 )
			.appendLiteral( ':' )
			.appendValue( MINUTE_OF_HOUR, 2 )
			.optionalStart()
			.appendLiteral( ':' )
			.appendValue( SECOND_OF_MINUTE, 2 )
			.optionalStart()
			.appendFraction( NANO_OF_SECOND, 3, 9, true )
			.optionalEnd()
			.optionalStart()
			.appendOffsetId()
			.optionalEnd()
			.appendLiteral( '[' )
			.parseCaseSensitive()
			.appendZoneRegionId()
			.appendLiteral( ']' )
			.toFormatter( Locale.ROOT )
			.withResolverStyle( ResolverStyle.STRICT );

	public static void main(String[] args) {
		ZonedDateTime withoutOffset = ZonedDateTime.parse( "2012-10-28T02:15:00[Europe/Berlin]", FORMATTER );
		ZonedDateTime withOffset = ZonedDateTime.parse( "2012-10-28T02:15:00+02:00[Europe/Berlin]", FORMATTER );

		if ( ! Objects.equals( withOffset, withoutOffset ) ) {
			throw new RuntimeException( "1 failed" );
		}

		withoutOffset = ZonedDateTime.parse( "2012-10-28T02:15:00[Europe/Berlin]", FORMATTER );
		withOffset = ZonedDateTime.parse( "2012-10-28T02:15:00+01:00[Europe/Berlin]", FORMATTER );

		// Will fail because the default offset during DST overlap when not specified is (in this case) +01:00
		// Note: this doesn't fail in JDK8 because of JDK-8066982. Use JDK11 instead.
		if ( ! Objects.equals( withOffset, withoutOffset ) ) {
			throw new RuntimeException( "2 failed" );
		}
	}

}