DateHelper Tutorial

This tutorial provides an overview of the DateHelper class, which is part of the lightweight-component/aj-util library. The DateHelper class provides utility methods for working with dates and times in Java applications.

Introduction

The DateHelper class contains static methods for common date/time operations using Java 8's java.time API, including formatting, parsing, and conversion between different date/time types.

Main Features

• Thread-safe date/time formatting and parsing
• Conversion between legacy Date and java.time types
• Support for multiple standard date/time formats
• RFC1123 and ISO8601 timestamp generation
• Object to date conversion utilities

Standard Formats

1. TIME - "HH:mm:ss"
2. DATETIME - "yyyy-MM-dd HH:mm:ss"
3. DATETIME_SHORT - "yyyy-MM-dd HH:mm"
4. DATE - "yyyy-MM-dd"

Methods

1. Formatting Methods

1. formatDate(LocalDate date) - Format LocalDate to string
2. formatTime(LocalTime time) - Format LocalTime to string
3. formatDateTime(LocalDateTime dateTime) - Format LocalDateTime to string
4. formatDateTime(Date dateTime) - Format Date to string

2. Parsing Methods

1. parseDate(String dateStr) - Parse string to LocalDate
2. parseTime(String timeStr) - Parse string to LocalTime
3. parseDateTime(String dateTimeStr) - Parse string to LocalDateTime
4. parseDateTimeShort(String dateTimeStr) - Parse short format string to LocalDateTime

3. Type Conversion

1. localDateTime2Date(LocalDateTime localDateTime) - Convert LocalDateTime to Date
2. localDate2Date(LocalDate localDate) - Convert LocalDate to Date
3. toLocalDate(Date date) - Convert Date to LocalDate
4. toLocalDateTime(Date date) - Convert Date to LocalDateTime

4. Standard Timestamps

1. getGMTDate() - Get current time in RFC1123 format
2. getISO8601Date() - Get current time in ISO8601 format

5. Utility Methods

1. object2Date(Object obj) - Convert various object types to Date
2. nowDateTime() - Get current Date
3. now() - Get current time as formatted string
4. now(String format) - Get current time with custom format
5. nowShort() - Get current time in short format

Usage Examples

Formatting Dates

LocalDateTime now = LocalDateTime.now();
String formatted = DateHelper.formatDateTime(now); // "2023-01-15 14:30:45"

Parsing Dates

LocalDate date = DateHelper.parseDate("2023-01-15");
LocalDateTime dateTime = DateHelper.parseDateTime("2023-01-15 14:30:45");

Type Conversion

Date date = new Date();
LocalDateTime ldt = DateHelper.toLocalDateTime(date);
Date newDate = DateHelper.localDateTime2Date(ldt);

Standard Timestamps

String rfc1123 = DateHelper.getGMTDate(); // "Mon, 15 Jan 2023 14:30:45 GMT"
String iso8601 = DateHelper.getISO8601Date(); // "2023-01-15T14:30:45Z"

Object Conversion

Date fromLong = DateHelper.object2Date(1673793045000L);
Date fromString = DateHelper.object2Date("2023-01-15");
Date fromLocal = DateHelper.object2Date(LocalDateTime.now());

Conclusion

The DateHelper class provides comprehensive utility methods for working with dates and times, making it easier to format, parse, and convert between different date/time representations in Java applications.