import java.time.OffsetDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Locale;
 
class Main {
 
    private static final DateTimeFormatter FORMATTER = DateTimeFormatter.ofPattern(
            "uuuu-MM-dd'T'HH:mm:ssX", Locale.ENGLISH);
 
    public static void main(String[] args) {
        OffsetDateTime odt = OffsetDateTime.parse("2018-12-30T06:00:00Z");
 
        // Default format
        System.out.println(odt);
 
        // The custom (desired) format
        String formatted = odt.format(FORMATTER);
        System.out.println(formatted);
    }
}

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