How do you format dates in Java?

Table of Contents

• Introduction
• Date Formatting Using SimpleDateFormat (Pre-Java 8)
  • 1. Using **SimpleDateFormat**
    • Example:
  • 2. Pattern Syntax in **SimpleDateFormat**
    • Example: Formatting a Date in Different Styles
• Date Formatting Using DateTimeFormatter (Java 8 and Later)
  • 1. Using **DateTimeFormatter** (Preferred in Java 8 and Later)
    • Example:
  • 2. Pattern Syntax in **DateTimeFormatter**
    • Example: Formatting a Date in Different Styles with DateTimeFormatter
  • 3. Locale-Sensitive Date Formatting
• Conclusion

Introduction

In Java, formatting dates to display in a human-readable or specific format is a common requirement. Depending on your Java version and the libraries you use, there are multiple ways to format dates. The two most common approaches are using the SimpleDateFormat class (for pre-Java 8 code) or using the DateTimeFormatter class introduced in Java 8 as part of the java.time API. In this guide, we’ll explore both approaches and show how to format dates for different patterns and locales.

Date Formatting Using SimpleDateFormat (Pre-Java 8)

1. Using **SimpleDateFormat**

SimpleDateFormat is a legacy class used for formatting and parsing dates in a specific pattern. It allows you to define patterns using letters, where each letter represents a part of the date or time (e.g., yyyy for year, MM for month, dd for day).

Example:

Output:

In this example:

• yyyy represents the year (4 digits).
• MM represents the month (2 digits, with leading zero).
• dd represents the day of the month (2 digits).
• HH represents the hour of the day in 24-hour format.
• mm represents minutes.
• ss represents seconds.

2. Pattern Syntax in **SimpleDateFormat**

Here are some commonly used patterns:

• yyyy: Year (e.g., 2024)
• MM: Month (e.g., 03 for March)
• dd: Day of the month (e.g., 13)
• HH: Hour in 24-hour format (e.g., 14)
• mm: Minutes (e.g., 45)
• ss: Seconds (e.g., 30)
• a: AM/PM (e.g., PM)

Example: Formatting a Date in Different Styles

Output:

Date Formatting Using DateTimeFormatter (Java 8 and Later)

1. Using **DateTimeFormatter** (Preferred in Java 8 and Later)

Starting from Java 8, the DateTimeFormatter class in the java.time package provides a modern and more flexible way of formatting and parsing dates. It works seamlessly with the LocalDate, LocalTime, LocalDateTime, and other classes from the java.time API.

Example:

Output:

In this example, the pattern "yyyy-MM-dd HH:mm:ss" formats the LocalDateTime into a string representation.

2. Pattern Syntax in **DateTimeFormatter**

The pattern syntax in DateTimeFormatter is quite similar to SimpleDateFormat:

• yyyy: Year
• MM: Month
• dd: Day
• HH: Hour in 24-hour format
• mm: Minutes
• ss: Seconds
• a: AM/PM

Example: Formatting a Date in Different Styles with DateTimeFormatter

Output:

3. Locale-Sensitive Date Formatting

DateTimeFormatter can also be used with locale-specific formatting to handle date formats based on regional settings.

Output:

Conclusion

In Java, formatting dates can be done in various ways depending on the version and the libraries you use. For legacy code, SimpleDateFormat is still commonly used, but it has limitations and has been largely replaced by the more powerful DateTimeFormatter in Java 8 and later. The java.time API is now the preferred choice for formatting dates and times due to its flexibility, clarity, and thread-safety.

Whether you're using SimpleDateFormat for legacy applications or DateTimeFormatter for modern Java, knowing how to format dates and times effectively is a crucial skill for Java developers working with date-based data.