How to use date and time functions for date calculation and formatting in Java

How to use date and time functions for date calculation and formatting in Java

In Java, date and time are very common and important data types. In order to facilitate the processing of dates and times, Java provides a wealth of date and time functions that can perform date calculation, formatting and other operations. Below is a detailed introduction to how to use date and time functions in Java, along with code examples.

1. Date calculation

1. Get the current date
   Use the java.time.LocalDate class to get the current date. The sample code is as follows:

   import java.time.LocalDate;
   
   public class DateCalculation {
    public static void main(String[] args) {
        LocalDate currentDate = LocalDate.now();
        System.out.println("当前日期：" + currentDate);
    }
   }

2. Date addition and subtraction operations
   You can use the plus() and minus() methods to add dates Subtraction operation. The sample code is as follows:

   import java.time.LocalDate;
   import java.time.temporal.ChronoUnit;
   
   public class DateCalculation {
    public static void main(String[] args) {
        LocalDate currentDate = LocalDate.now();
        LocalDate nextDay = currentDate.plus(1, ChronoUnit.DAYS);
        LocalDate previousYear = currentDate.minus(1, ChronoUnit.YEARS);
        System.out.println("当前日期：" + currentDate);
        System.out.println("明天的日期：" + nextDay);
        System.out.println("去年的日期：" + previousYear);
    }
   }

3. Calculate the difference between dates
   You can use the java.time.temporal.ChronoUnit class to calculate the difference between two dates gap. The sample code is as follows:

   import java.time.LocalDate;
   import java.time.temporal.ChronoUnit;
   
   public class DateCalculation {
    public static void main(String[] args) {
        LocalDate startDate = LocalDate.of(2022, 1, 1);
        LocalDate endDate = LocalDate.now();
        long daysBetween = ChronoUnit.DAYS.between(startDate, endDate);
        System.out.println("开始日期：" + startDate);
        System.out.println("结束日期：" + endDate);
        System.out.println("两个日期之间的天数差距：" + daysBetween);
    }
   }

2. Date formatting

1. Format the date as a string
   Use java.time The .format.DateTimeFormatter class can format dates into strings. The sample code is as follows:

   import java.time.LocalDate;
   import java.time.format.DateTimeFormatter;
   
   public class DateFormatting {
    public static void main(String[] args) {
        LocalDate currentDate = LocalDate.now();
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
        String formattedDate = currentDate.format(formatter);
        System.out.println("格式化后的日期：" + formattedDate);
    }
   }

2. Parsing a string as a date
   Use the java.time.format.DateTimeFormatter class to parse a string into a date. The sample code is as follows:

   import java.time.LocalDate;
   import java.time.format.DateTimeFormatter;
   
   public class DateFormatting {
    public static void main(String[] args) {
        String dateString = "2022-01-01";
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
        LocalDate parsedDate = LocalDate.parse(dateString, formatter);
        System.out.println("解析后的日期：" + parsedDate);
    }
   }

The above is a code example of using date and time functions for date calculation and formatting in Java. Through these functions, you can easily perform date calculation and formatting operations to facilitate processing of various date needs.

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