How to get the current time in JAVA

JAVA method of obtaining the current time: 1. Using the Date class, you can use the no-argument constructor of the Date class to create a Date object representing the current time, and then use the "toString()" method of the object to Convert to string representation; 2. Use the Calendar class to obtain the values ​​of the current time's fields such as year, month, day, hour, minute, and second; 3. Use the new time and date API to provide a more concise and easy-to-use and thread-safe way to handle dates and times.

In Java, to obtain the current time, you can use the Date class, Calendar class in the Java standard library, and the new time and date API introduced in Java 8 (java. time package). These three methods are described in detail below.

1. Use Date class:

Date class is a class used to represent date and time in the Java standard library. To get the current time, you can use the no-argument constructor of the Date class to create a Date object representing the current time, and then use the object's toString() method to convert it to a string representation.

import java.util.Date;
public class GetCurrentTime {
    public static void main(String[] args) {
        Date currentDate = new Date();
        System.out.println(currentDate.toString());
    }
}

Run the above code and the string representation of the current time will be output, for example: "Thu Sep 28 05:39:11 UTC 2023".

2. Use the Calendar class:

The Calendar class is a class in the Java standard library for processing dates and times. The Calendar class can be used to obtain the values ​​of the current time's fields such as year, month, day, hour, minute, and second.

import java.util.Calendar;
public class GetCurrentTime {
    public static void main(String[] args) {
        Calendar calendar = Calendar.getInstance();
        int year = calendar.get(Calendar.YEAR);
        int month = calendar.get(Calendar.MONTH) + 1; // 月份从0开始，需要加1
        int day = calendar.get(Calendar.DAY_OF_MONTH);
        int hour = calendar.get(Calendar.HOUR_OF_DAY);
        int minute = calendar.get(Calendar.MINUTE);
        int second = calendar.get(Calendar.SECOND);
        
        System.out.println("Current Time: " + year + "-" + month + "-" + day + " " + hour + ":" + minute + ":" + second);
    }
}

Running the above code will output the year, month, day, hour, minute, and second values ​​of the current time, for example: "Current Time: 2023-9-28 5:39:11".

3. Use the new time and date API (java.time package):

Java 8 introduces a new time and date API, located in the java.time package. This API provides a more concise, easy-to-use and thread-safe way to handle dates and times. Among them, the LocalDateTime class represents a date and time without a time zone.

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
public class GetCurrentTime {
    public static void main(String[] args) {
        LocalDateTime currentDateTime = LocalDateTime.now();
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        String formattedDateTime = currentDateTime.format(formatter);
        
        System.out.println("Current Time: " + formattedDateTime);
    }
}

Run the above code and the formatted string representation of the current time will be output, for example: "Current Time: 2023-09-28 05:39:11".

Summary:

In Java, you can use the Date class, Calendar class and the new time and date API (java.time package) to get the current time. Use the Date class and Calendar class to get the values ​​of various fields of the current time, and use the new time and date API to get the formatted string representation of the current time. Developers can choose the appropriate method to obtain the current time based on specific needs.

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