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        final Options options = new Options();

        final Option nameCmdOption = Option.builder("n").hasArg(true).argName(NAME_CMD_OPTION).longOpt(NAME_CMD_OPTION).desc("Person's name").required(true).type(String.class).build();
        options.addOption(nameCmdOption);

        final Option surnameCmdOption = Option.builder("s").hasArg(true).argName(SURNAME_CMD_OPTION).longOpt(SURNAME_CMD_OPTION).desc("Person's surname").required(true).type(String.class).build();
        options.addOption(surnameCmdOption);

        final Option ageCmdOption = Option.builder("a").hasArg(true).argName(AGE_CMD_OPTION).longOpt(AGE_CMD_OPTION).desc("Person's age").required(true).type(Integer.class).build();
        options.addOption(ageCmdOption);

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        try {
            final CommandLine cmd = new DefaultParser().parse(PersonalInfoReader.createCommandLineOptions(), args);

            if (cmd.hasOption(HELP_CMD_OPTION)) {
                new HelpFormatter().printHelp(120, "java", "Person Parsing", PersonalInfoReader.createCommandLineOptions(), "");
                return;
            }

            final String name = cmd.getOptionValue(NAME_CMD_OPTION);
            final String surname = cmd.getOptionValue(SURNAME_CMD_OPTION);

nikkatsa

public class SingletonClass {

    private static final com.nikoskatsanos.nkjutils.yalf.YalfLogger log = com.nikoskatsanos.nkjutils.yalf.YalfLogger.getLogger(SingletonClass.class);

    private SingletonClass() {
        log.info("Initializing %s", this.getClass().getName());
    }

    public static final SingletonClass getInstance() {
        return SingletonClassHelper.INSTANCE;

nikkatsa

public Person(String name, String surname, int age, String email) {
        this.name = name;
        this.surname = surname;
        this.age = age;
        this.email = email;
}

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public static class PersonBuilder {

        private static final Pattern EMAIL_VALIDATION_REGEX = Pattern.compile("^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}$");

        private String name;
        private String surname;
        private int age;
        private String email;

        private PersonBuilder() {

nikkatsa

@FunctionalInterface
public interface NowService {

    /**
     * @return the number of milliseconds since 1st January 1970 UTC
     */
    long nowMillis();

}

nikkatsa

public class SystemClockNowService implements NowService {

    @Override
    public long nowMillis() {
        return System.currentTimeMillis();
    }
}

nikkatsa

public class NamedThreadFactory implements ThreadFactory {

    private final String name;
    private final boolean isDaemon;
    private final AtomicInteger threadCounter;

    public NamedThreadFactory() {
        this("Thread");
    }

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public void start() {
        final ExecutorService left = Executors.newSingleThreadExecutor(new NamedThreadFactory("Left", true));
        final Object leftObject = new Object();
        final ExecutorService right = Executors.newSingleThreadExecutor(new NamedThreadFactory("Right", false));
        final Object rightObject = new Object();

        left.execute(() -> {
            while (true) {
                synchronized (leftObject) {
                    ThreadUtils.sleepWithoutInterruption(3000L, TimeUnit.MILLISECONDS);

nikkatsa

public enum Weekdays {
    MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY
}