Maven coordinates of dependent class libraries: ```xml <dependency> <groupId>joda-time</groupId> <artifactId>joda-time</artifactId> <version>2.10</version> </dependency> ``` Joda Time is a date and time processing library designed for the Java programming language. It provides support for operations related to date, time, interval, duration, etc., and has a simple and easy-to-use API. Compared to Java's native date and time processing class library, Joda Time is more flexible and powerful. The following is an example code implementation: ```java import org.joda.time.DateTime; import org.joda.time.Hours; import org.joda.time.Days; import org.joda.time.Months; public class JodaTimeExample { public static void main(String[] args) { //Get the current time DateTime now = DateTime.now(); System. out. println ("Current time:"+now); //Get the time before the specified hour DateTime hoursAgo = now.minus(Hours.hours(2)); System. out. println ("Time two hours ago:"+hoursAgo); //Obtain the time after the specified number of days DateTime daysLater = now.plus(Days.days(5)); System. out. println ("Five days later:"+daysLater); //Obtain the time before the specified number of months DateTime monthsAgo = now.minus(Months.months(3)); System. out. println ("Three months ago:"+monthsAgo); } } ``` Summary: Joda Time is a very powerful and popular Java date and time processing library. By using Joda Time, we can easily obtain the time before and after a specified hour, day, or month. Using Joda Time, we can more easily handle dates and times, eliminating the need to rely on Java's native date and time processing class library, thereby improving development efficiency.

Joda Time is a Java date and time processing class library, which is used to replace the date and time classes in the Java Standard library. It has a simpler and easier to use API, supports handling time in different time zones, and provides some convenient methods for calculating and manipulating dates and times. Firstly, we need to add the Joda Time dependency in the Maven configuration file of the project: ```xml <dependency> <groupId>joda-time</groupId> <artifactId>joda-time</artifactId> <version>2.10.12</version> </dependency> ``` Next, let's implement a simple example of converting the time of one time zone to the time of another time zone. Assuming we have a time string and a representative string of two time zones, we want to convert that time from one time zone to another. ```java import org.joda.time.DateTime; import org.joda.time.DateTimeZone; import org.joda.time.format.DateTimeFormat; import org.joda.time.format.DateTimeFormatter; public class TimeZoneConversionExample { public static void main(String[] args) { //Input time string String dateTimeString = "2021-01-01T00:00:00"; //Enter the time zone of the time string DateTimeZone inputTimeZone = DateTimeZone.forID("America/Los_Angeles"); //Target Time Zone DateTimeZone outputTimeZone = DateTimeZone.forID("Asia/Tokyo"); //Create Joda Time object for input time DateTime inputDateTime = DateTime.parse(dateTimeString, DateTimeFormat.forPattern("yyyy-MM-dd'T'HH:mm:ss").withZone(inputTimeZone)); //Time converted to target time zone DateTime outputDateTime = inputDateTime.withZone(outputTimeZone); //Output Results System. out. println ("Input time:"+inputDateTime); System. out. println ("Output time:"+outputDateTime); } } ``` In the above code, we used Joda Time's DateTime class to represent a time object and the DateTimeZone class to represent different time zones. Firstly, we parse the input time string through the DateTimeFormatter and specify the input time zone. Then, use the withZone method to convert the time object to the time of the target time zone. Finally, print out the input and output times through the output statement. Finally, to summarize, we can easily achieve time conversion between time zones by adding Joda Time's Maven dependency and using its provided DateTime and DateTimeZone classes. At the same time, using Joda Time can avoid some issues that exist in Java standard date and time classes, and provide a simpler and more user-friendly API.

Joda Time is an alternative Java date/time class library for the Java programming language. It provides simpler, more flexible, and more powerful date and time processing capabilities. Firstly, we need to add the dependency of Joda Time in Maven. The Maven coordinates of Joda Time are as follows: ```xml <dependency> <groupId>joda-time</groupId> <artifactId>joda-time</artifactId> <version>2.10.10</version> </dependency> ``` Joda Time contains many useful classes, the most important of which is the DateTime class. The following is an example code for formatting dates using Joda Time: ```java import org.joda.time.DateTime; import org.joda.time.format.DateTimeFormat; import org.joda.time.format.DateTimeFormatter; public class JodaTimeExample { public static void main(String[] args) { //Create a DateTime object that represents the current date and time DateTime currentDateTime = new DateTime(); //Define Date Time Formatter DateTimeFormatter formatter = DateTimeFormat.forPattern("yyyy-MM-dd HH:mm:ss"); //Format Date Time String formattedDateTime = formatter.print(currentDateTime); //Output formatted date time System.out.println("Formatted DateTime: " + formattedDateTime); } } ``` Running the above code will output the formatted result of the current date and time, for example: 'Formatted DateTime: 2021-05-20 15:30:00'. Summary: Using Joda Time allows for simpler and more flexible handling of dates and times in Java. We can use the 'DateTime' class to represent dates and times, and the 'DateTimeFormatter' class to format dates and times. Joda Time provides many other useful classes and methods for convenient calculation and operation of dates and times.

The Apache Commons Lang Library provides a time formatting class library. This class library provides some tool classes and methods that can be used to process and format dates and times. The Maven coordinates of the dependent class library are: ```xml <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-lang3</artifactId> <version>3.12.0</version> </dependency> ``` The following is a complete example of using Apache Commons Lang Library for time formatting, which is used to convert the current time to the specified format and output it to the console: ```java import org.apache.commons.lang3.time.DateFormatUtils; import java.util.Date; public class TimeFormattingExample { public static void main(String[] args) { Date currentDate = new Date(); String formattedDate = DateFormatUtils.format(currentDate, "yyyy-MM-dd HH:mm:ss"); System.out.println("Formatted Date: " + formattedDate); } } ``` In the above example, we first imported the 'org. apache. commons. lang3. time. DateFormatUtils' class and the' java. util. Date 'class. Then, we created a 'Date' object called 'currentDate', which contains the current date and time. Next, we use the 'DateFormatUtils. format()' method to convert the 'currentDate' object into a string in the specified format and store it in the 'formatedDate' variable. Finally, we print the formatted date string to the console. Summary: The Apache Commons Lang Library in the Apache class library provides easy-to-use tool methods for easily formatting dates and times. Using this library, we can convert the date object into a specified formatted string. In this way, we can easily process and display dates and times in Java applications.

1. Maven coordinate dependency: ``` <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-lang3</artifactId> <version>3.12.0</version> </dependency> ``` 2. Introduction to the Apache Commons Lang class library: Apache Commons Lang is a Java class library from the Apache Software Foundation that provides many utility classes for handling common operations such as strings, numbers, dates, files, IO, collections, and more. Among them, the 'DurationFormatUtils' class provides some methods for handling time differences. 3. Java code implementation example: The following is a sample code for calculating time difference using the Apache Commons Lang class library: ```java import org.apache.commons.lang3.time.DurationFormatUtils; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Date; public class TimeDifferenceExample { public static void main(String[] args) { String startTime = "2021-01-01 12:00:00"; String endTime = "2021-01-02 10:30:00"; SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); try { Date startDate = format.parse(startTime); Date endDate = format.parse(endTime); long durationMillis = endDate.getTime() - startDate.getTime(); String durationFormatted = DurationFormatUtils.formatDuration(durationMillis, "HH:mm:ss"); System.out.println("Time difference: " + durationFormatted); } catch (ParseException e) { e.printStackTrace(); } } } ``` In the above code, we first defined the start time and end time strings. Then use the 'SimpleDateFormat' class to convert the string into a 'Date' object. Next, calculate the millisecond difference between two 'Date' objects to obtain the number of milliseconds of the time difference, and then use the 'DurationFormatUtils' class to format the milliseconds as a time difference string in the form of' HH: mm: ss'. Finally, print out the time difference string. 4. Summary: By using the Apache Commons Lang class library, we can easily calculate time differences and format them into specific display formats. It provides many convenient tool classes that can simplify common operations in Java applications. In the above example, we used the 'DurationFormatUtils' class to format the time difference, and the' formatDuration 'method can convert milliseconds into a specific format of the time difference string.

Google Guava is a Java class library that provides several user-friendly, efficient, and carefully designed tools and collection classes to simplify some common tasks in Java programming. This includes time calculation. Before starting to use Google Guava for time calculation, it is necessary to add the corresponding dependency library to the project. Here are the Maven coordinates of Guava: ```xml <dependency> <groupId>com.google.guava</groupId> <artifactId>guava</artifactId> <version>30.1-jre</version> </dependency> ``` By adding the Maven dependency mentioned above, the Guava class library can be introduced into the project and its time calculation function can be used. Here is a complete example of using Guava for time calculation: ```java import com.google.common.base.Stopwatch; import java.util.concurrent.TimeUnit; public class TimeCalculationExample { public static void main(String[] args) throws InterruptedException { Stopwatch stopwatch = Stopwatch.createStarted(); //Simulate time-consuming tasks Thread.sleep(2000); stopwatch.stop(); long elapsedMillis = stopwatch.elapsed(TimeUnit.MILLISECONDS); System. out. println ("Task execution time:"+elapsedMillis+"milliseconds"); } } ``` In the above code, we first created a 'Stopwatch' instance for timing. Then use the 'start()' method of 'stopwatch' to start the timer and execute a time-consuming task (using 'Thread. sleep (2000)' here to simulate a time-consuming operation). Finally, use the 'stop()' method of 'stopwatch' to stop the timer and use the 'elapsed()' method to obtain the task execution time. By specifying the Unit of time of the 'elapsed()' method as' TimeUnit. MILLISECONDS', we obtain the millisecond representation of the task execution time. Summary: When using Google Guava for time calculation, we can easily perform timing operations through the 'Stopwatch' class. Create a timer instance using the 'createStarted()' method, start the timer using the 'start()' method, stop the timer using the 'stop()' method, and obtain the task execution time using the 'elapsed()' method. We can specify the return Unit of time to better show the task execution time.

Maven coordinates of dependent class libraries: ```xml <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-lang3</artifactId> <version>3.12.0</version> </dependency> ``` FastDateFormat is a class in the Apache Commons Lang library, which provides a fast and Thread safety method for formatting and parsing dates and times. It is an improvement of SimpleDateFormat in Java, with better performance and Thread safety. The following is a complete Java code example that demonstrates how to use FastDateFormat for date and time formatting: ```java import org.apache.commons.lang3.time.FastDateFormat; import java.text.ParseException; import java.util.Date; public class FastDateFormatExample { public static void main(String[] args) { //Get current date Date currentDate = new Date(); //Define date format String pattern = "yyyy-MM-dd HH:mm:ss"; //Format Date String formattedDate = FastDateFormat.getInstance(pattern).format(currentDate); System.out.println("Formatted Date: " + formattedDate); //Parse Date try { Date parsedDate = FastDateFormat.getInstance(pattern).parse(formattedDate); System.out.println("Parsed Date: " + parsedDate); } catch (ParseException e) { e.printStackTrace(); } } } ``` Output: ``` Formatted Date: 2022-01-01 12:34:56 Parsed Date: Sat Jan 01 12:34:56 CST 2022 ``` Summary: FastDateFormat provides a fast, Thread safety way to format and parse dates and times. It is a better choice than the built-in SimpleDateFormat in Java, especially for high-performance requirements in multi-threaded environments. When in use, you can obtain an instance through the getInstance() method and pass the date format pattern for formatting and parsing operations.

In Java, the SimpleDateFormat class can be used to format dates. Before using SimpleDateFormat, it is necessary to add the corresponding dependencies in the pom.xml file of the project. The Maven coordinates of the dependent class library are as follows: ```xml <dependency> <groupId>commons-lang</groupId> <artifactId>commons-lang</artifactId> <version>2.6</version> </dependency> ``` Briefly introduce the library: Commons lang is an open source project under the Apache Software Foundation that provides many commonly used Java tool classes. The DateUtils class provides methods for formatting and parsing dates. Implement the complete sample and write the complete Java code as follows: ```java import org.apache.commons.lang3.time.DateUtils; import java.text.SimpleDateFormat; import java.util.Date; public class DateFormatExample { public static void main(String[] args) { Date date = new Date(); SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd"); String formattedDate = sdf.format(date); System.out.println("Formatted Date: " + formattedDate); try { Date parsedDate = sdf.parse(formattedDate); System.out.println("Parsed Date: " + parsedDate); } catch (Exception e) { e.printStackTrace(); } // Using commons-lang DateUtils String formattedDate2 = DateUtils.format(date, "MM/dd/yyyy"); System.out.println("Formatted Date 2: " + formattedDate2); try { Date parsedDate2 = DateUtils.parseDate(formattedDate2, "MM/dd/yyyy"); System.out.println("Parsed Date 2: " + parsedDate2); } catch (Exception e) { e.printStackTrace(); } } } ``` The above code first creates a Date object for the current date. Then, use SimpleDateFormat to format the date and output the formatted date. Next, use SimpleDateFormat to parse the formatted date and output the parsed date. Finally, the code uses the DateUtils class of commons lang to format and parse dates, and the output result is the same as the previous method. Summary: Using SimpleDateFormat can easily format and parse dates, meeting most date format requirements. The DateUtils class in commons lang provides more functionality, making date processing more convenient. In actual development, suitable methods can be selected according to needs.