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Updated on 2025-03-06

Method of converting from Integer to Date in Java

How to convert from Integer to Date

In Java, if we have data of Integer and want to convert it to Date, we can use the following method to implement it. First, we need to make it clear that Integer represents a timestamp, that is, the number of milliseconds calculated from 00:00:00 GMT on January 1, 1970. Then you can use the Date class provided by Java or the new time class library in Java 8 (such as LocalDateTime) to convert it. Here is the example code for converting using the Date class:

## Sample code for converting Integer to Dateimport ;
public class IntegerToDateConverter {
    public static void main(String[] args) {
        Integer timestampInteger = 1614739200000; // Integer timestamp for the example, in milliseconds        // Convert Integer to a long-type time stamp        long timestamp = ();
        // Create a Date object and convert the timestamp to a Date object        Date date = new Date(timestamp);
        // Print the converted Date object        ("The converted Date object is:" + date);
    }
}

In the example code above, we first convert the timestamp of Integer to a timestamp of long type, and then use the constructor of the Date class to convert it to a Date object, thus implementing the conversion from Integer to Date. Please note that using the Date class for date operations is no longer recommended after Java 8. It is recommended to use a new time class library, such as the LocalDateTime class. Here is a sample code for converting using the LocalDateTime class:

## Example code for converting using LocalDateTimeimport ;
import ;
import ;
public class IntegerToLocalDateTimeConverter {
    public static void main(String[] args) {
        Integer timestampInteger = 1614739200000; // Integer timestamp for the example, in milliseconds        // Convert Integer to a long-type time stamp        long timestamp = ();
        // Convert timestamps to LocalDateTime class using Instant class        LocalDateTime localDateTime = ((timestamp), ());
        // Print the converted LocalDateTime object        ("The converted LocalDateTime object is:" + localDateTime);
    }
}

In this example, we use the new time class library in Java 8 to convert the timestamp of Integer type into a LocalDateTime object through the Instant class and the LocalDateTime class. In short, through the above example code, we can implement mutual conversion from Integer type to Date type, which facilitates the processing and operation of date and time in Java.

When encountering situations where the Integer type timestamp needs to be converted into a Date object, such as processing log data or displaying time information. The following is a simple practical application scenario to show how to convert Integer to Date and format output.

Application scenario description

Suppose we have an Integer type timestamp that stores the order creation time, which we need to convert to a Date object and output in the specified format.

Sample code

The following is a sample code based on this application scenario, demonstrating how to convert an Integer timestamp to a Date object and format the output according to the specified date and time format.

import ;
import ;
public class IntegerToDateConverter {
    public static void main(String[] args) {
        // Simulate an Integer type order to create a time stamp        Integer orderTimestamp = 1646208000000; // Corresponding to 2022-03-01 00:00:00        // Convert the timestamp of Integer type to long type        long timestamp = ();
        // Create a Date object        Date date = new Date(timestamp);
        // Create SimpleDateFormat object for formatting date output        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        // Format output date and time        String formattedDate = (date);
        // Output result        ("Order creation time is:" + formattedDate);
    }
}

Example description

  • We first define an Integer type order creation time stamporderTimestamp, and convert it to a time stamp of type long.

  • Then use the Date class to convert the time stamp of type long into a Date object, indicating the creation time of the order.

  • Create SimpleDateFormat objectdateFormat, the output format of the specified date and time is "yyyy-MM-dd HH:mm:ss".

  • use(date)Method formats the Date object to obtain the formatted date and time stringformattedDate。

  • Finally output the formatted order creation time. Through such sample code, we can implement the conversion from the Integer type timestamp to the Date object, and output it in the specified format, which facilitates the display and processing of time information in actual applications.

In Java, the Date class is used to represent date and time information. It can store the number of milliseconds since 00:00:00 GMT on January 1, 1970 and provides a method to operate date and time. However, it should be noted that after Java 8, it has recommended to use new time and date class libraries (such as LocalDateTime, ZonedDateTime, etc.) instead of the Date class, because there are some problems with the Date class, such as not thread-safe and not design-friendly enough.

The main features of the Date class

  • Store timestamps:The Date class stores the number of milliseconds since 00:00:00 GMT on January 1, 1970. You can pass the timestamp through the constructor or use the **setTime(long time)** method to set the time.
  • Date operation:The Date class provides methods to add and subtract dates and times, and can calculate and compare dates.
  • Format output:The SimpleDateFormat class can be used for formatted output of date and time.
  • Outdated methods:Some methods in the Date class have been marked out as outdated and are not recommended, which is more unfavorable to the processing of date and time.

Examples of basic usage of Date class

Here are some basic Date class usage examples:

import ;
import ;
public class DateExample {
    public static void main(String[] args) {
        // Create a Date object for the current time        Date currentDate = new Date();
        
        // Output the milliseconds of the current time        ("The number of milliseconds of the current time:" + ());
        
        // Use SimpleDateFormat for formatting output        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String formattedDate = (currentDate);
        ("Formatted output of current time:" + formattedDate);
        
        // Compare dates early and late        Date futureDate = new Date(() + 86400000); // The next day of the current time        ("Is the future time after the current time:" + (currentDate));
    }
}

Things to note

Although the Date class can still be used in Java, in real-time application development, it is recommended to use a new time and date class library, such as the package introduced by Java 8, which provides a more powerful, easy to use and thread-safe date and time class. Therefore, when developing new projects, it is recommended to avoid using the Date class directly, but use the new API to handle date and time-related operations.

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