CODEWITHSUNDEEP
javasimpledateformatdate-conversion
user2680017
user2680017

Reputation: 111

Date Conversion with ThreadLocal

I have a requirement to convert incoming date string format "20130212" (YYYYMMDD) to 12/02/2013 (DD/MM/YYYY)

using ThreadLocal. I know a way to do this without the ThreadLocal. Can anyone help me?

Conversion without ThreadLocal:

    final SimpleDateFormat format2 = new SimpleDateFormat("MM/dd/yyyy");
    final SimpleDateFormat format1 = new SimpleDateFormat("yyyyMMdd");
    final Date date = format1.parse(tradeDate);
    final Date formattedDate = format2.parse(format2.format(date));

Upvotes: 10

Views: 16264

Answers (3)

Arvind Kumar Avinash
Arvind Kumar Avinash

Reputation: 79015

Java-8+

The modern Date-Time classes introduced with Java-8 are thread-safe.

Demo:

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.Locale;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        DateTimeFormatter parser = DateTimeFormatter.ofPattern("uuuuMMdd", Locale.ENGLISH);
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd/MM/uuuu", Locale.ENGLISH);
        LocalDate date = LocalDate.parse("20130212", parser);
        String formattedString = date.format(formatter);
        System.out.println(formattedString);
    }
}

Output:

12/02/2013

Note that I prefer u to y with DateTimeFormatter.

Learn more about the modern Date-Time API from Trail: Date Time.

Upvotes: 1

Richie
Richie

Reputation: 9266

ThreadLocal in Java is a way to achieve thread-safety apart from writing immutable classes. Since SimpleDateFormat is not thread safe, you can use a ThreadLocal to make it thread safe.

class DateFormatter{

    private static ThreadLocal<SimpleDateFormat> outDateFormatHolder = new ThreadLocal<SimpleDateFormat>() {
    @Override
    protected SimpleDateFormat initialValue() {
        return new SimpleDateFormat("MM/dd/yyyy");
    }
};

private static ThreadLocal<SimpleDateFormat> inDateFormatHolder = new ThreadLocal<SimpleDateFormat>() {
    @Override
    protected SimpleDateFormat initialValue() {
        return new SimpleDateFormat("yyyyMMdd");
    }
};

public static String formatDate(String date) throws ParseException { 
    return outDateFormatHolder.get().format(
            inDateFormatHolder.get().parse(date));
}        
}

Upvotes: 11

Evgeniy Dorofeev
Evgeniy Dorofeev

Reputation: 135992

The idea behind this is that SimpleDateFormat is not thread-safe so in a mutil-threaded app you cannot share an instance of SimpleDateFormat between multiple threads. But since creation of SimpleDateFormat is an expensive operation we can use a ThreadLocal as workaround

static ThreadLocal<SimpleDateFormat> format1 = new ThreadLocal<SimpleDateFormat>() {
    @Override
    protected SimpleDateFormat initialValue() {
        return new SimpleDateFormat("yyyy-MM-dd");
    }
};

public String formatDate(Date date) {
    return format1.get().format(date);
}

Upvotes: 15

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