How to parse date and time in Java - using the SimpleDateFormat class

Java method of parsing dates and times - using the SimpleDateFormat class

During the development process, we often encounter the need to parse and process dates and times. Java provides many date and time related classes and methods, among which the SimpleDateFormat class is a very commonly used tool class for parsing and formatting dates and times.

SimpleDateFormat class is a class under the java.text package, through which we can convert the string representation of date and time into a Date object, or format the Date object into a string. Below we will introduce in detail how to use the SimpleDateFormat class for date and time parsing.

1. Format date and time
   First, we need to understand how to format date and time into a specific string format. The SimpleDateFormat class provides some predefined formatting modes and also supports custom modes.

The following are some common predefined formatting patterns:

• "yyyy-MM-dd": represents year-month-day, such as: 2021-01- 01
• "yyyy/MM/dd": indicates year/month/day, such as: 2021/01/01
• "yyyy-MM-dd HH:mm:ss": indicates year -Month-Day Hour:Minute:Second, such as: 2021-01-01 12:00:00
• "yyyy/MM/dd HH:mm:ss": indicates year/month/day hour:minute :Seconds, such as: 2021/01/01 12:00:00

The following are some symbols used for custom modes:

• "yyyy": means four Year with two digits, such as: 2021
• "MM": Represents a two-digit month, such as: 01
• "dd": Represents a two-digit date, such as: 01
• "HH": indicates the number of hours in the 24-hour format, such as: 12
• "mm": indicates the number of minutes, such as: 00
• "ss": indicates the number of seconds, Such as: 00

The following is a simple example to format the current date and time into the specified string format:

import java.text.SimpleDateFormat;
import java.util.Date;

public class DateFormatExample {
    public static void main(String[] args) {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String formattedDate = sdf.format(new Date());
        System.out.println(formattedDate);
    }
}

Run the above code, the current date and time will be output The formatted result, for example: "2021-01-01 12:00:00".

2. Parsing date and time
   In addition to formatting date and time into strings, we often need to parse strings into Date objects. The SimpleDateFormat class also provides parsing methods corresponding to predefined formatting patterns.

The following is a sample code for parsing date and time:

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateParseExample {
    public static void main(String[] args) {
        String dateString = "2021-01-01 12:00:00";
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

        try {
            Date date = sdf.parse(dateString);
            System.out.println(date);
        } catch (ParseException e) {
            e.printStackTrace();
        }
    }
}

Run the above code to parse the output string into the result of a Date object, for example: Fri Jan 01 12:00: 00 CST 2021.

It should be noted that the parse method of SimpleDateFormat may throw ParseException, so we need to handle exceptions in the code.

In actual development, SimpleDateFormat also provides many other methods, such as:

• setTimeZone(TimeZone zone): Set the time zone
• setLenient(boolean lenient): Set whether to tolerate parsing
• format(Date date): Format the Date object into a string

We can flexibly use these methods according to actual needs.

Summary
SimpleDateFormat class is a common tool class for parsing dates and times in Java. Through it, we can convert string representations of dates and times into Date objects, or format Date objects into strings. . This article introduces the basic usage of SimpleDateFormat, including methods for formatting dates and times and parsing dates and times. I hope this article can help you better understand and use the SimpleDateFormat class.

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