Tests how to parse LocalDateTime with DateTimeFormatter

DateTimeFormatterExample.java

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class DateTimeFormatterExample {
    public static void main(String []args) {
        DateTimeFormatter pattern = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSS");
        LocalDateTime time = LocalDateTime.parse("2018-07-30T18:15:34.823", pattern);

        System.out.println("parsed time: " + time.toString());
    }
}

output.txt

parsed time: 2018-07-30T18:15:34.823

regexp_example output

It matches

regexp_example.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class RegexpExample {
    public static void main(String []args) {
        String timeString = "2018-07-30T18:15:34.823";
        String pattern = "\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2}.\\d{3}";

        Pattern r = Pattern.compile(pattern);
        Matcher m = r.matcher(timeString);

        if (m.matches()) {
            System.out.println("It matches");
        } else {
            System.out.println("It doesn't match");
        }
    }
}

regexp_example_with_date_time_formatter.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class RegexpExampleWithDateTimeFormatterPattern    {
    public static void main(String []args) {
        String timeString = "2018-07-30T18:15:34.823";
        String pattern = "yyyy-MM-dd'T'HH:mm:ss.SSS";

        Pattern r = Pattern.compile(pattern);
        Matcher m = r.matcher(timeString);

        if (m.matches()) {
            System.out.println("It matches");
        } else {
            System.out.println("It doesn't match");
        }
    }
}

regexp_example_with_date_time_formatter.output

It doesn't match